Originally Posted by LesterOfPuppets

I rode 40 miles in the rain over the weekend and didn't bring a bottle at all. I was well hydrated beforehand and had a litre of mineral water when I got home.
100 mile ride through mostly populated areas, I'll bring one 1-litre bottle, refill 2 or 3 times.
50 mile ride in summer through the desert, I'll bring one 1-litre bottle liquid and a frozen 2-litre bottle.