I used to go to school at Michigan State University, and I worked in the cafeteria. They had milk in bags there. Each bag was about 5 gallons, very heavy, and made of slippery plastic. Pity the fool who dropped or punctured one!

We'd have to replace them in the milk dispenser when they went empty, and there was an extremely dangerous step in which the new bag needed to be opened. You had to carefully clamp the nozzle of the bag with a fork or two, cut open the tip, worm the tip through the dispenser's lever, and finally remove the fork. If the lever wasn't seated just right, or you didn't pinch the plastic just perfectly, you had to clean up several gallons of milk off the floor and dispenser.