If your cat has diarrhea, it is important to switch to a bland diet that is easy to digest and won't irritate its stomach. This may include boiled chicken or turkey, plain white rice, or a commercial low-fat, high-fiber cat food recommended by your veterinarian.
Last, avoid feeding your cat dairy products, fatty foods, and anything that might upset its stomach. Make sure your cat has access to plenty of fresh water, and consider giving it probiotics. So, that it can help restore the balance of healthy bacteria in its gut.