Overpriced tap water.
The item id for Bottled Water in unturned is 14. You can use this ID with the commands below to spawn the item, give it to a player or buy it on a modded economy server.
Useable: Consumeable
Size_X: 1
Size_Y: 1
Size_Z: 0.4
Water: 55
Blueprints: 1
Blueprint_0_Type: Repair
Blueprint_0_Supply_0_ID: 392
Blueprint_0_Supply_0_Amount: 1
Blueprint_0_Build: 27
ConsumeAudioClip: Sounds/DrinkSwallow.mp3