Melavai

So sorry you had the heat exhaustion!!

A couple of general rules that my DH and I use-

Drink every time you think about it. My DHdrinks a lot more than I do, but after 85 degrees, I go through a lot more water than when it is cooler.

Eat at least 200 calories per hour if the ride is going to be longer than 1 1/2 hours/20 miles. This is advice we've gotten from the Carmichael coaches, and has served us well on long rides and events, especially. Your body stores enough glycogen for about an hour and a half, then you are running on empty.

Use electrolytes!
I actually like shot blocks.... I eat them on many of my rides.
I use NUUN sometimes, I like the fizziness. My DH doesn't like the artificial sweetener.
I like GU Brew lemon flavor - it's got calories and electrolytes both, and seems lighter than something like Gatorade

My DH likes endurolytes for electrolytes. He is susceptible to cramps and thinks it helps him.

I really can't ride much if it's hot, especially if it's humid- so in summer in Tucson I need to finish my rides by 8-9 am. I have had several experiences with heat exhaustion, feeling faint, and have to find some kind of shade (not always easy in Arizona!!) and pour water over my head, sometimes need to lie down. I have only needed to be rescued once, but now I plan my hot weather rides to avoid the conditions that have gotten me in trouble.

We stop at Circle K stores, Quick Marts etc and fill our bottles with lots of ice and a little water. They don't seem to mind, although we do often buy a little item or two.