It would have been even worse than outside, because in those days the tanks weren't like the ones I served in, the kind we have today.
I'm a tanker myself, and nowadays we have air conditioning in tanks, which is really required in these hot climates. It would have been even hotter, and I dare say that everything was hot. The water you drank, the food you ate, you wouldn't even need to heat it, it would have been heated already.
Very often they would put their cans of meat on the engines, and that would warm them. It was very uncomfortable. You would have to drink gallons of water every day. First, you would have to acclimatize yourself to these conditions. Our troops in Afghanistan now, and those who fought there during the combat phase, went through the same very difficult conditions.
The weariness at the end of the day is unbelievable. You have the stress of the enemy, you're extremely tired, and you're sweating profusely. Guys would lose many pounds. If you want to lose weight, it's one way of doing it. It's very difficult.