How do you stave off food comatose after lunch?
khafra: Eat protein and increase your dopamine production, which is a "happy and alert" neurotransmitter (http://frank.mtsu.edu/~studskl/food.html).  Going heavy on the carbohydrates spikes your serotonin, and if they're simple carbohydrates your insulin vs. blood sugar will suck the energy right out of your brain in an hour.  Ergogenics like Adrafinil are a more extreme and expensive alternative to caffeine, but cheap nootropics like Piracetam or Vinpocetine may do the trick, if dietary changes alone don't.