Check this out. Disregard the diet stuff and do the formula to see how many calories a day your body requires. It might surprise you.
Metabolism Calculator
I don't know much about nutrition but I always try to eat a good breakfast and lunch and go heavy on the meat with both. Peanutbutter is good but take it easy on the jelly. For quick energy snacks I like those little boxes of raisins or a couple of bags of peanuts. I try to stay away from sugar snacks after lunch...when the sugar wears off it makes me feel draggy.
I like to carry coffee in the winter and Gatorade is good any time. I've tried Red Bull and those 5 Hour Energy things and all they did was make me jittery with no real increase in energy. I try to stay hydrated.
Now, all that being said and despite all my good advice about avoiding sugar and eating healthy...I still like to stop in the morning on the way to the woods and have some plain old ordinary 7-11 coffee. And Donettos. If there aren't any Donettos an eclair will do just fine.