In some ways, the thirst level in Metal Gear Survive is even more important than hunger. While hunger does determine how much health you have, the thirst level determines your max stamina gauge, and it can only be refilled by consuming clean water, which is rather difficult to find.
Clean water can be obtained in a variety of ways. You could potentially receive a free bottle as a daily login bonus, or by scouring the environment for sealed bottles containing them. However, for the most part, you’ll find lots of dirty water around the environment. This can still help to refill your stamina gauge, but it can also make you ill and result in a lot of adverse effects.
Thankfully, you will be able to craft clean water out of dirty water once you obtain the hanging pot. To get it, simply play through the single-player campaign until you reach chapter 7. Completing the chapter will reward you with the hanging pot blueprint, and you’ll be able to craft it back at base camp. With this item, you’ll now be able to boil water and make clean water whenever you want.
Be sure to search for Twinfinite for more information on Metal Gear Survive.