"Hot"

I can't imagine it was much worse than what I experienced in my tank in Iraq. It's not as if today's tanks necessarily have air conditioning either. Short sleeves are certainly appreciated! We drink a lot of water.

I was recently inside an M3 Grant, which had a water tank located where the radio would have been on an American vehicle. So depending on the tank, some crews would have had reasonable access to what would, obviously, have been warm water. Otherwise, they'd do the same thing we did: Climb out and get at the water in the bustle or sponson stowage. Water is, of course, very heavy, but on a tank, it's light because the tank's carrying the weight around.

There is also, obviously, the 25A/C option. Open the hatch, stick your head out, and cool down a bit at 25mph.