Potion of Watchful Rest
Potion, common
When you drink this potion, you gain the following benefits for the next 8 hours: magic can’t put you to sleep, and you can remain awake during a long rest and still gain its benefits. This sweet, amber-colored brew has no effect on creatures that don’t require sleep, such as elves.
Source: Waterdeep: Dungeon of the Mad Mage p. 62