reduce junk carbohydrate intake… cut out as much high fructose corn syrup as possible. eat many small meals a day instead of two or three big ones. up good carb intake, like fruits and whole grains. eat as lean as possible, but you still want 30% of your calories to come from fat. eat nuts, fish, and other sources of natural, unprocessed fats.
none of these things are going to give you the immediate energy of caffeine or other stimulants, but you won’t get the crash either.