I've been taking cold showers before bedtime. My shampoo has been all warm and runny from the weather. I suppose that means I've been doing the opposite. But the cold showers are interesting. When I get in the water feels warm on my legs and arms, and cold on my torso thanks to the differences in core temperature versus extremities -- a very odd sensation. But after a little bit my core cools down. Then I don't dry off quite completely and go to bed under the ceiling fan so evaporation keeps me cool long enough to fall asleep.

I like the idea of frozen soaps, but I'd probably find the direct application of something at that low a temperature to be uncomfortable. And I don't use shower gel...