Hi there, I am one who almost always drinks boiled water when I water fast.
It's the only thing I want. If you drink it on the hot side, it becomes more cleansing/eliminating. Cold would be the last thing I'd want, even in mid-summer--when I am water fasting, that is. For me, it just keeps me warm enough, and soothed. I have fasted 29 and 21 days, and then several shorter ones.
In the first three days I allow myself some green tea, plain, maybe one a day, at night, seems to be when I really want it, but not after three days. Once over that hump, then it's just plain water to the end.