Experienced and professional animal trainer provide their insights in answering this question :
A. She may have stomach problems like excessive acid production. It may be worth to try a trial treatment for that and see if it is going to help .

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

If your dog is suffering from liver disease, they may have bad breath because of the reduced functioning of the liver. If it cannot filter out toxins, the result is bad breath. Dogs with liver failure often have breath that smells like a dead animal.
Dental Health Concerns

One of the most common reasons for bad breath in dogs is underlying health concerns and conditions. These dental health issues that affect your dogs can range from conditions such as tooth decay to gum disease and oral infections.

Liver disease can cause foul, sweet, musty breath. Diabetes can cause the breath to smell sweet (similar to pear drops or nail polish remover). Lumps/masses in the mouth often become infected and smell.
Kidney Disease

If your pup`s bad breath smells like feces or urine, it may be a sign that they have recently eaten poop (which is another common problem that should be investigated by your vet) or a symptom of kidney issues.

Start a Routine to Stop Stinky Dog Breath

Maintaining a routine of regular at home brushing and seeing a professional for twice yearly deep cleanings, is the best way to ensure your pet`s mouth stays fresh, clean, and free from bad bacteria.

Supplementing your pup`s regular diet with a probiotic formulated specifically for dogs can help balance healthy oral bacteria and keep breath smelling fresh. Check with your vet about the best brand of probiotics for your dog and an appropriate dosage.
In some cases, stress and anxiety in dogs can lead to problems with bad breath. The reason is that dogs experiencing stress can suffer from gastrointestinal problems, vomiting, excessive drooling, and destructive chewing.
The most common causes of bad breath in dogs are bad oral hygiene and periodontal disease. Just like in humans, the build-up of plaque and tartar can lead to the development of the bacteria that cause bad breath.
Severely ill patients often have characteristic smells. Patients with diabetic ketoacidosis have the fruity smell of ketones, although a substantial number of people are unable to detect this. Foetor hepaticus is a feature of severe liver disease; a sweet and musty smell both on the breath and in urine.
That`s why it`s important to never share your own mouthwash with the dog – not even a splash in their water dish is OK. Ingredients in human mouthwash, ranging from xylitol (very toxic to pets) to fluoride can make dogs sick.
Why does my dog`s breath smell like fish? A dog`s breath can rarely be described as fresh or pleasant, but if your dog smells of fish then it could be a sign of dental issues (infection, tooth decay, abscesses or gingivitis), digestive problems, kidney disease or diabetes.
Are carrots safe for me to feed my dog?” While some of the vegetables we love are unsafe to feed our dogs, carrots are a perfectly safe and nutritious treat for your dog.
Give dogs one-to-three tablespoons of yogurt per day depending on size. Plain, Greek style yogurt is best. Make sure that you don`t feed yogurt sweetened with xylitol.
Giving your dog a small amount a day (we`ll get to exactly how much later) can help combat “dog breath” – as long as you`re also following a regular oral hygiene routine. These are good reasons to add manuka honey into your dog`s diet proactively. However, manuka honey is also very effective when used reactively.
Immune health: Peanut butter provides a healthy dose of vitamin E, a powerful antioxidant. Plus, it`s full of immune-boosting B6. These keep your dog`s immune system running in tip-top shape, helping your pup defeat the yucky oral bacteria build-ups that cause bad breath.
A natural source of natural probiotics for dogs is yogurt or kefir. You`ll want a product high in live cultures with no added sugar or artificial sweeteners. Added sugars aren`t healthy for dogs, and some artificial sweeteners, like xylitol, are toxic for dogs.
Some vets learn in school that puppy breath is caused by a still-developing esophagus leaking gas from the stomach. But there is such a thing as bad puppy breath which can be caused by an impacted tooth the beginnings of gum disease worms or eating poop. (Yes dogs do that.)
Dog breath is rarely fragrant, but if your dog has suddenly developed rancid breath, he/she could be dehydrated. One reason that odors occur is lack of enough saliva, and since water is needed to make saliva, this condition warrants a visit to the vet.
Frequent bathing can help control odor. Arthritis and other health conditions can make it difficult for your dog to properly groom himself, which can cause his fur and skin to smell funky over time. Weekly shampooing or visits with a professional groomer can help. Impacted anal glands are also common in older dogs.
Symptoms of Fetor Hepaticus

These distinctive changes to the smell of your breath often alert doctors to liver disease. You should contact a doctor if you have fetor hepaticus. You may need tests to check your liver functions.

One of the most often occurring reasons of digestive system bad breath is H. Pylori. It`s a sort of bacteria that often coexists with the other bacteria in your gut microbiome, but when things go awry, it can cause major damage. About two thirds of stomach ulcers and duodenal ulcers may be brought on by it.
Liver disease

Infections and diseases of the liver can produce high ammonia levels in the urine and the accompanying pungent odor. Ammonia levels in blood and urine will increase when the liver is not working as it should. Any continued ammonia odor in urine should be checked by a doctor.

When the excess urea in your body reacts with saliva, it forms ammonia–which you then exhale through your breath. If you have CKD, this is what gives your breath that ammonia scent. The medical name for this is “uremic fetor”.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. Do not know about his teeth but his breath is bad
ANSWER : A. Small dogs often develop tartar on their teeth, causing bad breath and inflammation of the gums. Your dog needs to have an exam with your vet to determine the cause of the bad breath. If it is indeed bad teeth/dental disease, he will also need bloodwork to determine his ability to handle anesthesia. If his bloodwork is good, he should have a dental cleaning and possibly extractions. Leaving his teeth as they are means that the inflammation and infection causing the bad smell will continue, and the bacteria in his mouth has a direct route to infect heart valves, a condition called vegetative endocarditis. Most dogs recover quickly and do great after a dental and extractions and live longer, healthier lives as a result.

Q. My senior cat has very bad breath. It smells like a dead animal.
His teeth were removed earlier this year so what else could cause this bad breath?
ANSWER : A. If hi doesn’t have bad teeth or/and gingivitis he may have problem with excessive acid production in the stomach or other gastrointestinal problems.

Read Full Q/A … : Symptoms of Stomatitis

Q. Are the dental sprays (to avoid dog plaque build-up) effective?
ANSWER : A. I disagree to some degree with my colleague below. Actual tartar that is already built up on the teeth is not removable with dental chews or brushing. Once the tartar is there the only way to get it off is to either hand scale the teeth or ultrasonically scale the teeth. The benefit with doing a dental is not only to remove the starter but to clean under the gumline which is where most dental disease starts. Once the teeth are clean, however, then you can prevent new tartar from sticking by daily brush and dental chews. In my experience the sprays are not effective but certainly it can’t hurt. The absolute best is professional dental cleanings the second-best is daily brushing and dental chews and the third best are water additives and sprays.

Q. My cocker spaniel horrible bad breath. & it looks like her entire gum line/inner lips look like it’s all a big canker sore. What is it & what do I do
ANSWER : A. Gum disease and tartar are quite common in Cockers. If he´s build up tartar the best treatment is Scale and Polish at your vet under general anesthetics, and normally we recommend antibiotics previously to reduce the infection around te teeth and do the dentals safely. The bad breath is produced by the bacterias eating from the food remaining on the teeth/gums. A good teeth brush will help as well and can prevent the tartar after your vet remove it.

Read Full Q/A … : Dog Oral Tumors

Q. My cat has bad breath & top lip exposed not sure if fang tooth is loose
ANSWER : A. If he has bad breath, he almost certainly has bad teeth. Many cats suffer with tooth pain, and their owners often don’t realize until after it’s treated how uncomfortable the cat must have been. Veterinarians can perform dental cleanings and extractions under anesthesia. I recommend you look into this option for your cat.

Read Full Q/A … : Cat Teeth

Q. My dog has just developed a terrible breath order what causes this and what can I do about it.
ANSWER : A. The most common reason of bad breath in cats are dental problems. You should take your cat to your vet for mouth examination and possibly teeth cleaning. If his/her mouth looks fine your vet will be looking for other causes of bad breath like infections or stomach problems.

Q. My cats k9 tooth fell out this morning. It doesn’t seem like she is in pain or discomfort but the area is swollen. What should I do?
ANSWER : A. If your cat is still a kitten it is possible she is losing her teeth as her adult teeth come in. This is very normal and may make her want to chew on objects a bit more as the adult teeth come in. Keeping her happy and eating should help, and if she is having any trouble, then moistening dry food with a little water or giving a wet food diet should help.

If your cat is an adult and losing teeth, it may indicate a gum issue or other illness which should be looked at by your vet as soon as possible to make sure the other teeth or gums are not badly affected. Until you can get to the vet, a wet food or moistened dry food diet can help keep her eating comfortably with minimal pain. You may want to keep the tooth to have your vet take a look as well.

Q. it is a pit her teeth are brown and dark what cause that
ANSWER : A. Dark and brown teeth are covered with tartar and possibly stains from the coloring or dyes put in dog food.
I would recommend brushing your pets teeth daily and also giving her a higher quality food which won’t stain the teeth so readily. Also feeding her a dry kibble instead of wet food will help the teeth as well.
If there is staining there this in most cases won’t be removed completely but getting your pets teeth cleaned and fluoride treated will remove the tartar and help keep your pets dental hygiene up to par.