What fluid do you drink on the moon?

Of course it is possible, but you had better be in a spacesuit (that has some built-in engineering allowing you to drink) or in some other kind of life supporting structure. There is gravity on the moon, although it is much less than earth gravity; moon gravity is roughly 17% of the gravity on earth. It would be possible to keep water in a cup, but quick movement would cause some unexpected dousings. If you are not in a spacesuit or another life supporting structure, then drinking water will be the least of your worries.