You can only do so much at daycare, it has to be at home as well. You could serve him only the most nutritious food, but if he is eating junk at home it negates all your good efforts. If you really want to help him, you are going to have to talk to his parents.

I am in a similar situation right now, I have a 3 year old dcg that apparently lives on juice at home (and not even real juice, the sugar-filled fruit punch type juice) and gets sent it in her lunch here everyday as well. I have to force her to drink water everyday because all she wants is her juice box. She is a skinny little thing, but I really think she is getting sugar overload everyday. She also told me she eats Lucky Charms for breakfast everyday too - lovely! So I am just getting my thoughts together now about how to bring up this discussion with her mom because I think it is really detrimental to her long term health. Don't mean to high jack the post, but I was just about to put my own post up when I saw this.