Chocolate Milk is an example of High Demand and Low Supply. At school cafeterias, they are used as a currency to trade lunches.
To obtain a Chocolate Milk, you can either A: Pay for it like a Scrub, or B: Trade an item of food of equal or more value in exchange for Chocolate Milk.
Having Chocolate Milk, you shouldn't drink it, as it, like all other School Lunch foods, is made of sodomized Toxic Waste. Instead, use it to bargain other people out of lunch items that you think look good. Those with the most Chocolate Milk cartons are the most powerful, and thus can barter for more food items.
Nolan: Hey, Jake, Can I have some of those Tater Tots?
Jake: Sure, but you gotta give me some of that Chocolate Milk
Nolan: Alright, Alright, you drive a hard bargain.
Nolan:*hands over milk*
Jake:*hands over tater tots*
Nolan: pleasure doing business with you, good sir.