I highly reccomend Clif Bars. Unlike other 'energy' bars out there, it is actually made of and tastes like real food. And unlike candy bars, it's actually pretty healthy. It's got good amounts of protein, complex carbs, fat, fiber, vitamins, and not too much sugar. If the bars are reallly old or in cold temperatures, they can be hard, but I'd take a stale Clif bar over a fresh bar of another brand any day.

If you're looking for a purely survival food, where volume is limited and caloric density is the main concern, they may not be the best choice, since a bar only has about 240 Calories. But if you want something convenient and healthy that makes a descent substitute for a meal, that you'll actually want to eat, give them a try.

If you shop around you can find them for $12 a box, which is $1 per bar.