What do you do to handle fatigue during a long tournament?

[freeringo]

My 2 big tourneys wins were 11 hours ($3 rebuy on Stars) and 9 hours i think for paradise.

I wasnt tired and they both finished at 10am my time nearly

Eejit uses an unlimited supply of addrenaline to handle his fatigue.
I don't have so much. Can I buy some?