Uh...This is the lightweight zone. I am tired just reading about how you are carrying sodas and ice packs. I prefer to leave the sodas at home...and camp in areas where these is snow to chill my aching bones...and any food I want cold.

But it you really want to do this...trying wrapping some mylar film around an envelope made of a closed cell foam sleeping pad.

Then you'll have to put that in your bear cannister or hang it carefully from a tree to keep the raccoons and bears from enjoying a nice cold drink on a hot summer's day.