- Emergency rations
- Survival food tabs
- Grocery store "energy bars"
- Long shelf life meat products, such as jerky or beef-stick
- Small cans of meat, such as tuna or chicken
Emergency rations are products like grocery store energy bars, only designed for very long shelf life, and a more complete nutritional profile. The big advantage to these is that you can stuff a few in your bag and you won't have to change them out for up to 5 years. They are light, small, and provide a good source of calories and vitamins for 3 days. Keep in mind, though, that although these will certainly keep you going for three days, you will still be hungry. The 3-day rations are based on 1200 calories a day, which is plenty to keep you up and functioning for three days, but you will still feel hungry. If you live in a place where it's cold outside, and you are going to be working, you may want to carry 2 sets. If you are outside in the cold and/or doing much work, 2400 calories a day will come much closer to being what your body needs. These kinds of rations were really developed for lifeboats and other situations where the assumption is that you'll mostly be sitting around.
Grocery store "energy bars" are good choices for survival situations, since they are tasty, and contain lots of calories as well as good nutrition. They do have to be changed out fairly regularly, though. I'd suggest replacing them at least every 6 months, and you may want to test them to see how they hold up to temperature changes. I keep my emergency kit in my car, where it can get either pretty hot or cold, so something that's going to melt in the heat wouldn't be a good choice.
"Survival food tabs" were designed for Special Forces, and so are meant to be very light and keep well. One bottle is supposedly a 15 day supply for one person, but again, keep in mind that you will be quite hungry. That ration is meant to keep you alive for 15 days, not keep you working. I believe that's only 240 calories a day for 15 days, plus a good supply of vitamins and minerals, etc. It'll keep you alive, but not working hard. However, they are very light, and are rated to keep for 10 years, so it might be a good addition.
Long-storage meat products. Things like jerky/pepperoni sticks, beef stick / summer sausage, or canned tuna or chicken are a good choice, as they are relatively light, high in protein, and calorie dense. They will have to be changed out at least every 6 months to a year for the jerky, etc. and probably every 1-2 years for canned meat. If you pack canned meat, remember a can opener, and keep in mind that cans are comparatively heavy. One thing to consider with meat products is the salt content. Things like jerky will make you very thirsty, and if all you have access to, is the water in your emergency bag, you will suffer. That's less of a problem with tuna or chicken, since the salt content is much lower, usually.