If your dog has fruity breath, it's time to make an appointment with your vet. Sweet, fruity-smelling bad breath may be a sign of canine diabetes, a metabolism disorder that affects your dog's blood sugar. It occurs when your dog produces too little insulin and requires lifelong treatment with a special diet, steady fitness regimen, and daily insulin injections. Other signs include decreased appetite, cloudy eyes, weight loss, excessive thirst, and frequent urination. Though diabetes isn't very common in dogs, it's still important to keep an eye out for any symptoms.