Me, personally? More times than I want to count, averaging once every June for the last 20 years or so.
I finally realized the truth in the saying that mental faculties are among the first things to go in heat exhaustion. Passing who-knows-how many fast food places and convenience stores because I was only 10 miles from home, for example. Last summer I caught myself in that situation just 2 miles from the house and stopped to buy some bottled water. Will I remember that lesson next month? (Wouldn't bet on it!)