Thirst

Thirst is displayed above your hunger bar. If your thirst bar runs out, you will start to take damage.

You can SHIFT+RightClick with an empty hand to drink from water blocks or the rain.

You can also drink from a Canteen and water bottles.

Drinking regular water may give you the Thirsty effect, so making Purified Water or Juice is a good idea.

Thirst, like Hunger, has saturation, so more valuable drinks will last longer.