Just using a LOT of water is a bad idea (unless you eat a good amount, with salt and other nutrients around that time). Because as we all know, this can lead to hyponatremia (at the risk of stating the obvious: you sweat out a lot of salt with the water you lose. Only replacing the water dilutes your blood (serum).
As altitude  increases, the air becomes less dense because of the smaller amount  of air above that altitude. There is a corresponding decrease in  pressure with an increase in altitude. Eventually you reach a point  without air, and the pressure decreases to zero. That is space. + 91 others found this useful.
Thus vertical air motions act to heat the lower atmosphere and cool the higher. The combined effect of those, as a few people mentioned, is that temperature on the average decreases with altitude in the troposphere-at a rate of 6.5 Â°C per km (3.6 Â°F per 1000 ft.). Yet the lapse rate varies depending on conditions.