Juice can be bought from Teimo's Shop for 12.95 mk per canister. The primary use for the juice canisters is to store kilju. Just press while looking at a canister to drink it empty, then pick it up and submerge it in the kilju bucket. The empty juice canisters can be retrieved from the landfill site once sold.
The brand of the juice in game is Mehukonna ("Juice frog"), and the canister has a picture of a frog on it. It is a parody of the real life Finnish juice brand Mehukatti ("Juice cat").