Know the signs of heat exhaustion and dehydration so you can articulate the ones you observed that led you to break the window.
My EDC knife has a window punch. I've used it once, and it works way better than I thought it would (ie, don't put a lot of muscle behind it and put your hand into the broken glass...)
https://www.amazon.com/Kershaw-Black.../dp/B0074FIPEM