How to stay awake? Sheer willpower. Yep. The amount of caffeine, sugar, loud music, etc. makes no difference to me (I routinely have Metallica or Linkin’ Park playing when I go to bed, so loud obnoxious music really makes no difference). For me, if I want to stay awake, I’ll stay awake until my body absolutely refusing to let me be awake any longer…usually at the 30+ hour mark.
Having something to do — a lot of something to do — will also do it. So, for Blogathon specifically — having a theme that will keep me working the whole time, volunteering as a monitor and occasional guest poster to fill in the time when my writing partner is posting, chatting in IM/iRC, playing on my RPG boards, participating on other thonners’ sites, having something to do with my hands in a crafty sort of way when I need to rest my eyes from the screen, having people drop by, watching movies, getting up and just dancing around when it’s either get up or pass out.
Mostly, as long as the brain’s active, the body forgets it needs sleep.