we have two season.....hot....cold....that's it

Started using insulated water bottles. Pack them with ice before the ride, makes a huge difference.

Interesting. For the last 12-15 years I used at least 10 different kinds of insulated bottles. Plastic foam insulated, stainless vacuum insulated, you name it. When actually drinking, the cool water tastes better, but it does not help cool me down. IN fact drinking cold water requires more calories to warm up the water.
I stopped using insulated bottles a couple of years ago. Warm water is just as good, but not the taste. I was OK yesterday at 105F with ambient air temp water. Plain bottles hold more liquid and are lighter. I have a few kinds of one liter bottles.
Two liters of water and one other fruit drink is enough for me, even on most centuries. Slowing down in the heat helps me the most.