I tend to carry low moisture foods and enough water to prepare them... but then again, I've also got a Coleman stove and fuel in the back of the Suburban to prepare them on. Canned goods can and will freeze if it gets cold enough, and as such, they'll bulge or burst... not the kind of mess you want in your back seat or trunk. For the short term, jerky and energy bars could probably cover you for a few days, and if you're stuck in your car in the middle of Winter for longer than that, food's not gonna be your biggest problem.

Troy