Under certain circumstances, such as when sleeping or fast travelling right before the hydration level reaches the trigger point, the player can skip this trigger point and become dehydrated. There is no way to forcibly take a drink, nor does the canteen ever run out of water the five-minute timer starts when the canteen is placed in the player's inventory (not, interestingly, when a save is loaded) and runs in the background, even while the Pip-Boy is up. There is no animation for taking a drink, nor does it interrupt any other action amusingly, it can even happen while the Courier is attacking an enemy in V.A.T.S, or while the courier is under water. An on-screen notification will tell the player when this happens. As long as this canteen is kept in the player's inventory, the Courier will take a sip from it every five minutes, restoring 15 HP and lowering dehydration by 25 in Hardcore mode.
