Frozen fuel

I can attest that shot blocks get very stiff and hard to chew.<br><br>
One possibility is to go for something that won't change. Smarties (tm) or the giant versions you can find in bulk are just compressed glucose powder. I would bet they don't change much and I've never had blood sugar problems with them when I'm already in the "burn anything available" mode.<br><br>
If you want to keep the contents of your waterbottle liquid, ethyl alcohol is a good antifreeze, just sayin' <img alt="smile.gif" src="http://files.kickrunners.com/smilies/smile.gif">

Another possibility: do potatoes freeze hard? It's possible that the old ultra standby - boiled potatoes - might stay chewable a little longer.<br><br>
You might do everyone here a favor by trying a number of things and letting us know what works best.