>>35580101Different species of Pokemon eat different things. When it comes to wild Pokemon, some have been confirmed to eat plants; some have been confirmed to eat other Pokemon; and all of them can eat berries.
Meanwhile, Pokemon who live with humans probably eat differently than their wild counterparts. Trained Pokemon would have access to kibble, pellets, and other types of special Pokemon food developed by humans. However, some trained Pokemon might still eat plants and/or meat to some extent. Also, it's likely that not all species of Pokemon would be able to handle processed food, so I think trainers would usually avoid giving human food to their Pokemon.