There's a rule of thumb that humans can go three minutes without air, three days without water and three weeks without food - but who wants to test that rule?
Certain foods have a long shelf life, taste good, and pack a wallop when it comes to calories. Understanding some humans have allergies and may need to look elsewhere, nuts and dried fruits, peanut butter, and canned fish are the types of foods that are examples of good-to-have foods on hand - high in nutrition and they don't need to be cooked. If cooking is an option, for example when sheltering in place, rice and pasta have a long shelf life and are packed with calories.
For a go bag, nuts and dried fruits as well as nutritional bars work great. They're light weight, they're neatly packaged and can be well balanced meals. There's a huge variety so even the most sensitive diet can most likely be accommodated.
In our home, we’ve isolated an area of our closet for emergency food and we have an inventory list which includes expiration dates for each item. Our goal is to have on hand 2000 calories per person - per day - for thirty days. An example of the density of calories and protein - one 48 ounce can of peanut butter has 8,000 calories and 300 grams of protein. It doesn't take much room at all and good to know we won’t be testing the rule if the time comes.