If I found out that a child I cared for usually traded their lunch for others' cookies and candy, I would probably first determine why they are trading their lunch for candy. Maybe they don't like the lunch they are currently eating? Do they need to learn about how to eat healthy? Assuming the child traded their lunch for others' food simply as a taste preference, I would explain to them that it isn't fair to take others' dessert because it doesn't give everyone a chance to have one. Then, I would also teach the child that it isn't healthy to not eat their lunch. After this, I would work on enforcing that the child I care for eat their own lunch and desserts.