Best foods for the brain?

My husband is 26 going to be 27 year old man and he does not eat normal foods! I would like to get him to eat fruits and veggies and meat and healthy things but he refuses. All he will eat is PBJ's mac and cheese, spaghetti with red sauce and parm. cheese , pepperoni pizza is the worst he could eat that every day. He will eat French fries with ketchup, french toast, peanut butter on its own or with toast and cereal. I want him to start eating better but he refuses to change can anyone give me any help with this??