Hi. We were there in June. The milk is poured from decantures but the Chocolate milk is in cartons (you have to ask for it). I don't remember seeing any juice boxes, but I didn't ask for any. They have many items that are kept in the back. We often got the chocolate milk and Diet Caffeine Free Coke and bottled beer at night. I would suggest asking for anything you want. It can't hurt and they might be able to get some for you. They are very nice and willing to help. I've seen people fill up plastic bottles, etc to take into the parks. Nobody cares or takes notice. I sure wish I had brought some small ziplock bags to take some extra snacks (like the goldfish crackers) into the parks with us!
Have a great trip and enjoy the view of Wishes from the Lounge! Spectacular!!!!