Domminate the room, do what i do, get one of those 15L water cooler bottles and bring it to class slung over one shoulder, slam that ♥♥♥♥♥♥♥♥♥♥♥♥ on the ground in the aisle.

Everytime you feel a little thirsty stand up, lift the bottle to your mouth with both arms, make sure you spill plenty of water over yourself and the floor every time you do, also, let out a deep, loud, exhalation of satisfaction after every sip, then finish the routine by slamming the bottle on the ground again before loudly saying, "pfew, I needed that, I was getting a bit THIRSTY" yell thirsty as loud as you can.

When class finishes, pick up the bottle in such a way that the remainder pours out as you leave the room.