The water...
I realise it was probably done for comedic effect (and it worked) but if you are crossing the desert in the boiling midday sun who the hell drops their full water bottle on the ground? I forget who dropped it now but he could of at least offered it to the other two before dropping it. I think if memory serves it was Chevy Chase who dropped it. Then he offers the other two lip balm lol
This is a very funny film, love it.