Don't bother. I doubt you'll be able to eat. Def eat some food before hand though. I bought a huge slice of pizza at a festival and maybe got one or two bites down. Ended up handing pieces of it out to hungry people.
http://www.youtube.com/watch?v=ibiCg0BRTnA
Saw that kid at roo 09. Hadn't slept in over a day driving there. Should have gotten a good night sleep but the energy level was good and I dosed my brains out with some real clean liquid. Was just happy I wasn't this kid. Wondered around and explored the farm for a really long time.