Wine Sack Water Bottle

I was reading Brett's review of the Platypus 2L water bottle and was reminded of a recommendation made to me by epic inflatable sea kayaker Audrey Sutherland: use an empty wine sack from one of those cheapo boxed wines. She said they are indestructable, strong enough to use as pillows. I've always wanted to find one, but have never seen such wine here in Japan. I was thinking that if you hooked up a hydration tube to the spigot then you might have a nice hydration system.