Well, maybe you don't consider it food, but its the most important thing you can take along. Don't even think of starting on a hike that takes you more than a mile from home without a bottle of water along. You should have at least two quarts of water with you and drink 1/2 to 1 cup every 30 to 45 minutes. Keep the water coming into your body even if you don't really feel very thirsty. If you are hiking, you are losing moisture and you need to replenish it.
By the end of a 4 hour hike, you should have drunk both quarts of water and you should be able to use the toilet. If you don't need to, then all that water came out as perspiration and you still need to drink more water to stay hydrated. After a hike, you should drink additional water until you need to use the toilet. I don't mean chug it down, I mean drink a 1/2 cup or so every 5 minutes or so.
Number One – GORP (Good Old Raisins & Peanuts). The best way to get gorp is make it yourself with your favorite foods, including M&M's, chocolate chips, mini marshmallows, Cheerios, cereal, raisins, peanuts, cashews…
Number Two - Energy bars. Sports nutrition energy bars are an excellent food source out on the trail. They pack a lot of calories in a small, heavy bar. Having the shelf life of plutonium, balanced nutrition, lightweight, almost no trash, and tasting great, they are almost the perfect food.
Number Three - Dried fruits. Dried fruits scored higher than fresh fruit because they are more durable, there is a lot less trash to pack out, and they pack more caloric bang per ounce. Raisins, dried cranberries, dried apricots, and dried apples aree favorites. Dried fruits are packed with carbohydrates and offer a quick energy fix. They are also flexible enough to be used with peanut butter or cheese..
Water is needed to digest dried fruits - if you don't drink it, you'll get dehydrated digesting the fruit. Fruit contains good vitamins and calories with very little fat.
Number Four - Tuna and Crackers. Grain is also a good source of carbohydrates. Breads and crackers are a good choice for day hikes.
Tuna fish contains high protein and is a good meal with cheese on crackers if you like the taste of tuna. Make sure you get one of the smaller cans of tuna that has a pull top to open, that way you won't need a can opener. To make things even more tasty consider smearing your tuna salad on a bagel (pre sliced) or into some pita bread. Nutritional pluses, tuna is almost pure protein while being balanced with carbohydrates from the crackers or bread.
Number Five- Fresh fruits. Nothing satisfies like a good apple, orange or pear. We recommend carrying fruit that can take rolling around in your backpack, you might find peaches, bananas, and plums less than desirable when you sit down to eat. They are known for natural carbohydrate fix, and almost everyone has a favorite fruit they will eat.
On day hikes, carrying a couple apples or other fresh fruit probably won't tip the scale on your pack and they include important water that you'd need to carry anyway.