What are some good (and sneaky) ways to get more vitamins and nutrients into a child's diet?

I've got some seriously picky kiddos and want to find a way to sneak more good stuff into the few things they will actually eat. My 9 yo daughter will not eat any fruit or vegetables but apples. I've tried everything including offering money and force feeding them to her. She declined the money and threw up in the trash can when I forced her. Not one of my finer parenting moments but I am desperate! My son is not quite as picky but he isn't the best eater in the world either. They both love meat, turkey sandwiches, pizza, chicken nuggets, fries, Spanish rice with chicken, chicken noodle soup, cheeseburgers, pasta with no sauce and frozen cheese raviolis. That's it, they won't eat anything else but candy and ice cream. If anyone has ideas on how to sneak some more nutrients into these foods I would love some advice.