Dogs and cats will always eat plants, no matter how hard you try. In most cases, it’s to help with their digestion. For instance, cats eat grass to help them get rid of hairballs. Since they can’t digest it, they throw up, which helps to dislodge what is stuck in their stomach.u003cbr/u003eu003cbr/u003eOn the other hand, dogs eat plants to add plant material to their diet. You can prevent them from chewing on plants by adding chunks of pumpkin or sweet potato to their food and giving them something they like to chew on.