What do you eat?
edw519: Fresh fruit.  Lots and lots and lots of it.  Melon, citrus, grapes, berries in season, and IMHO, the hacker's 2 best friends: apples and bananas.  Bananas are nature's perfect answer to your question, as long as they are ready to eat (brown spots) and not too soft yet.  Freeze them for smoothies once they reach that point.  I carry them everywhere and always have them on hand for long coding sessions.  I eat little else besides fruit before dinner unless I have a lunch date.Fruit is expensive, but forget about that.  Pay for the best.  The long term cost of feeding your brain and body suboptimal fuel is much higher.No one I know can keep up with me.  I believe diet is a major reason.