well first off make sure they are organic as much as possible.
if you are eating berries or other exposed fruits it is mandatory they are organic
the best fruits are going to be citrus, berries, melons, tropical fruits. the one i don't recommend are apples since they are extremely modified and are heavy on pesticides and wax. also they are picked very unripe and ripen in transport so their nutritional value is super low unless you are growing them yourself