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.
Temperature increases as you gain altitude in the stratosphere and the thermosphere. Temperature decreases as you gain altitude in the troposphere and mesosphere. Air temperature varies in complicated ways with altitude. Near the Earth's surface, air gets cooler the higher you climb. As you climb a mountain, you can expect the air temperature to decrease by 6.5 degrees C for every 1000 meters you gain. This is called the standard (average) lapse rate. If air temperature is 30 degrees C at sea level as shown above, you can expect it to be around 10.5 degrees C at air altitude of 3000 meters because of the lapse rate. Plan an expedition! You are going to climb Mount Audubon in Colorado today!