Go to sleep 2 hours earlier than you normally do!
It's easy to fall into the sleep deprivation trap and think you're getting more out of yourself, even when you're really not. I've always found the need to sleep at all very frustrating, so this lesson is hard-learned for me.
I'm still in love with my 36 hour hackathons, but now most days I'm trying to get enough sleep to feel energetic all day without in assistance from drugs like caffeine and nicotine.
My way of getting those 6 solid hours was a common hacker solution to the problem: I used the hours between 9 pm and 3 am, when no one could interrupt me.