If a cat vomits undigested cat food and yellow liquid, and its appetite is normal, it's generally considered to be due to eating too quickly or gastritis. Treatment suggests giving the cat oral broad-spectrum antibiotics specifically formulated for pets to control the gastrointestinal inflammation, along with medications to promote the recovery of the digestive tract mucosa and protect the gastrointestinal tract. If the cat has a strong appetite and doesn't vomit afterward, you can feed it small amounts of soaked cat food cereal, following the principle of small, frequent meals. 
What causes cats to vomit?
1. Some middle-aged and older cats may vomit due to long-term irregular diet or stress.
2. If a cat eats something inappropriate that causes neurological symptoms, it may vomit. For example, if a cat eats rat poison or other poisons that can cause nerve paralysis, it will vomit.
3. Cats may also vomit when they suffer from concussion, fractures, or internal bleeding due to external injuries.
4. Bacterial gastroenteritis, parasitic gastroenteritis, fungal gastroenteritis, allergic gastroenteritis, viral gastroenteritis, intestinal obstruction, foreign body gastroenteritis, megacolon, etc., can all cause vomiting in cats.
5. The owner keeps some flowers and plants at home, which may cause allergic gastroenteritis in some more sensitive cats, and then cause vomiting.
