Stealing Snacks

I am at my wits end with my SS6. He will wake up in the middle of the night and steal cookies, candy any kind of sweets we have in the house. Last night he got into the box of candy my husband bought for me before I even got to have any and ate all of them. I really don’t know what to do I’ve never withheld sugar or junk food in our house and we have a pretty well balanced diet between sugar and healthy so I don’t know WHY he’s doing this??? But it can’t continue we are far from wealthy and I cannot afford to continue to replenish the snacks on a daily basis because he’s selfish and wants to eat them all but I don’t want to stop buying them either because it isn’t fair to the other children who don’t steal food. He’s also an extremely picky eater and won’t eat vegetables most fruits beans nuts meats etc basically anything that isn’t Junk good but I also can’t just give him junk food all the time???! I’m seriously in the closet crying right now because I don’t know what to do.