Vault 13 Canteen

 is a miscellaneous item in Fallout: New Vegas.

Characteristics
The canteen will be able to store a certain amount of water from any water source. This will help with dehydration in Hardcore mode. It will give you more than one drink. If not in hardcore mode, and the canteen is in the player's inventory, you will periodically received a message at the top left corner; "You take a sip from your trusty Vault 13 canteen."

The canteen seems to trigger the player's drink and subsequent notification when the H2O meter reaches a certain level (something just under 200 where dehydration would set in). However, under certain circumstances - such as sleeping right before the hydration level reaches the trigger point - the player can "jump past" the trigger point and become dehydrated. The canteen will not work again until the player lowers their hydration level below the trigger point again via some other means.