PERSONALLY, I never drink cold or ice water when performing, and much prefer room temperature water ...in fact, I drink room temp water almost all the time ...
I CAN sing (however good or bad I might sound ) with a piece of a 'lozenge' in my mouth and prefer HALLS Mentho-Lyptus cough drops to keep my throat moist and nasal passages clear ...

Hydration is always important, but as for the 'benefit' of iced drinks during a performance, of course there are varied opinions as one can tell from this article:
https://music.stackexchange.com/questions/3124/is-cold-water-bad-for-the-throat