This also applies to the ending of the add-on ending screen.

If the timing is right, the on-screen notice will appear during the game's ending.

It can be seen in use while the Courier is attacking an enemy in V.A.T.S., while the Courier is underwater, or even when the Courier dies.

There is no special animation associated with drinking from the canteen, as with other first aid items, the screen notice, slight HP increase, and H 2O meter drop are the only indications it is working. As long as the canteen is kept in the Couriers inventory, they will take a sip from it every five minutes, restoring 15 HP and lowering Dehydration by 25.The font used for the '13' is different from the font used in Fallout and Fallout 2.Aesthetically, the canteen appears as a hip flask surrounded in a fabric coating featuring a '13' in distinctive Vault jumpsuit coloring.It can now also be acquired by purchasing the add-on Courier's Stash or by having the Fallout: New Vegas Ultimate Edition, which includes all add-ons. Originally, the only way to acquire this item was by redeeming the code that came with the pre-order exclusive Classic Pack. Under certain circumstances, such as when sleeping or fast traveling right before the hydration level reaches the trigger point, the player character can skip this trigger point and become dehydrated. The five minute timer starts when the canteen is placed in the Courier's inventory (not when a save is loaded) and runs in the background, even while the Pip-Boy is up. There is no way to forcibly take a drink, nor does the canteen ever run out of water.

An on-screen notification will tell the player character when this happens. As long as the canteen is kept in the Courier's inventory, they will take a sip from it every five minutes, restoring 15 HP and lowering Dehydration by 25 in Hardcore mode.

Fallout nv vault 13 canteen