It's abnormal for kittens to have bad breath. Kittens' diets are relatively simple, and their mouths usually have a milky or slightly fishy smell. If you notice bad breath in a kitten, it's not normal. You need to check if the kitten has oral diseases or digestive problems. Common causes of bad breath in kittens may include viral infections, stomatitis, oral ulcers, constipation, indigestion, bloating, or food accumulation in the stomach. 
Solutions for bad breath in kittens
1. The kitten needs a physical examination to determine the cause of its bad breath. If the bad breath is caused by a viral infection, the kitten will need to be treated with antibiotics and antiviral drugs, as well as given supplements to boost its immunity.
2. If a kitten develops ulcers or stomatitis in its mouth, it needs to have its mouth cleaned daily with saline solution, and medication for treating ulcers should be sprayed on the affected area. At the same time, vitamins and antibiotics should be administered.
3. If a kitten has indigestion, you can feed it some probiotics to regulate its digestive system, encourage it to drink more water, and gently massage its abdomen to help with digestion.
