[jeffnc]

As mentioned, most of the ideas in this thread are crap. You don't need any particular "hydration" sitting at a table for hours. Unless you are actually sweating profusely from nervousness or something. You need LESS "hydration" than normal office work where you'd be up and around. And certainly way less than any "sport" where you're actually moving.

You feel tired after a long period of mental exertion not because you've burned a lot of calories, but because your brain is simply tired, and sometimes because you're tense and your muscles might actually be tight. But that's a separate issue. It's not necessary to feel stressed just because you're concentrating.

Just eat regular food at regular intervals. Or if you are a person who has blood sugar going up and down, then eat smaller meals and snacks more often. Or eat lighter, more easily digested foods. Heavier meals take blood flow to your stomach and intestines and can make you feel lethargic or sleepy sometimes.

A sports drink such as Ultra Fuel would be more appropriate than the simpler-sugar in Gatorade.

(Of course each person is different. If you are into Adkins or some other diet because your body reacts to complex carbohydrates as if they were simple sugars, then "lighter meals" of carbohydrates might mess with your blood sugar, but you know who you are and you don't need this thread to tell you how you feel.)

An energy drink (or simply coffee or one NoDoz pill) can help with some caffeine intake. But sugar isn't necessary, and certainly extra water isn't going to do you any good (other than the fact that a lot of people don't drink enough water for optimal health to begin with), and extra electrolytes certainly are not needed (again, except for the fact that the diet of many people contains too much sodium relative to potassium and magnesium to begin with.)