Take a look at your pet's teeth and gums. Dingy teeth or red, swollen, or bloody gums could signal that it's time for some dental care. Use a child's toothbrush or a piece of gauze on your finger. Brush once a week, at least. If a brushing routine doesn't clear up the problem, you might have your vet take a look.
Digestive problems can also cause bad breath.
You may suspect this problem if you also notice loose stools or other signs of general poor health. Kidney problems often cause this type of breath odor. Consult your veterinarian immediately if you notice this type of odor on your pet's breath.