A Chihuahua's bad breath can be a common issue, but it could also indicate underlying health problems. A trip to the vet can help rule out any serious conditions causing the halitosis, such as dental disease or diabetes. Brushing your Chihuahua's teeth daily with special toothpaste and treats can help keep their mouth clean. Improving their digestion with more fiber and water in their diet can also combat bad breath. Holistic remedies like carrots, lemon water, parsley tea, and dill or peppermint leaves may provide some relief as well.