If you have not tried hammer gel you may like them if your into gels. No simple surgars like a lot of other gels so it gives you a mildly sweet taste with basically no surgar. Raspberry and Montana huckleberry are very very good. I have a hard time downing most gels but these taste like you are eating fruit.... this is if your a gel guy. They also make energy drink that is great as well. Not too sweet, no added surgar. All their stuff is organic and goes down smooth as well. I use their stuff exclusively for mountain biking and working out. But I Carry a few gel packets for quick, good tasting calories, along with some of their drink mix to throw in a nalgene. Hammer stuff is made for endurance athletes, not just to give you a quick boost.
Dehydrated fruit is a great snack, that is not too sweet. Dehydrated apples and a little tube of peanut butter is great on clean calories.
Recently I found all natural fig bars at walmart, dirt cheap, taste amazing. I have been running through a box or 2 a week. Again they are all organic, they go down, and come out smooth. They beat any energy bar out that I have ever tried.
Those are just some of my favorite, quick calorie foods. Lots of options if you like to sit down and eat, but these are my go to, on the go foods for biking, backpacking, running, hunting and fishing.
honestly your going to get the best "energy" out of nuts and dried fruit. if your looking for caffeine its going to be tuff to get away from sweets as they tend to go hand in hand with that kinda snack
x2 Justin's Peanut, almond, or hazelnut butter single packs. Trail mix with cranrasins and cashews. Hormel pre cooked bacon or pepperoni keeps well, also single serving spam packets. For caffeine I take the 200mg tablets.