If it's very hot and you have no water, at 45C you will die within hours, not days, especially if you are exercising and are not seeking any shade. It's not the pleasantest way to die, but it's not the worst either. Head off on foot, starting in the early morning, and keep going, heading in a direction away from other people. After 6 hours of that you won't be able to return alive, even if you want to. I suggested starting in the early morning, because that gives you a full day in the heat. Temperatures in a desert are usually much cooler at night. Drinking alcohol (spirts would be more effective than beer) would speed up the process, and might be an alternative to any painkiller.