A stillsuit is worn in the desert designed to absorb the body’s sweating and urination and to filter the impurities so that drinkable water in catch pockets could be sipped from a tube near the neck.
-DuneWiki
They don’t call it a CamelBak for nothing, although KhairAllah preferred to drink sweet well water deposited in the Sahara’s paleomonsoon rains, caused by a rotational wobble on the Earth’s axis 11,000 years ago, from a Qirba and let the camels carry it.