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I've never tried it. But I would point out that different brands of reservoirs are made of different plastics. I definitely would not try it with my older (1990s vintage) Platypus Big Zip, which has gotten brittle over time just by normal use. Drink tube materials have changed over the years too; typically they are laminated, and freezing could cause delamination. So be careful!
I try to make a weekly women's ride after work on Mondays, so Sunday afternoon I fill my 100 oz LUXE up with water, wrap the bite valve in foil (so no germies from the freezer attach and freeze it. In the morning I just stuff the bladder in the pack (doesn't always zip). It sits in my black car in 100 degree temps all day but by wheels down at 6:00 it is still cool.
I never use Gatorade/Cytomax, etc in my Camelbak. Just good ol' tap water, not sure that may make a difference.