Firstly, begin by changing your cat's diet to a more natural home-cooked cat food so that your cat's digestive system does not have to work as hard to digest the food. If after a week of changing its diet your cat's stools remain soft, try adding a half-teaspoon of Metamucil to each of its meals for two days. You can also give your cat unflavored Pedialyte, an electrolyte beverage, to make up for the nutrients lost due to diarrhea.