And the next day was presentation of your achievements.
And the day after back to normal.
First day, I "hackathoned" from 9 to 5 and went home. I didn't win...
I imagine the winner of this hackathon was the plucky and passionate new hire, fresh out of college, who narrowly managed to save the day, the company, and our american way of life, by: waterboarding the CTO for hours to obtain a confession that both founders and the entire board are complicit in a vast terrorist conspiracy, and then proceeded to execute both founders, kill the board, strangle the interns (one of them had a beard), kick the office puppy, shoot all the competitor's salespeople in the knees (thus helping secure a sale to a major new customer), and disarm the EMP.
And honestly, younger me probably would have thought it was fun, but 30yo me with a wife and kid was more "f this shit, you're not getting 12h of my family time without compensation."
I thought hackathons were dumb in college (most people just cheat and bring pre-baked projects) and it's still dumb after that.
If you want to get out of it, just send an email explaining your health and productivity is implicitly tied to your sleep. Worst case just do what I did and get a doctor's note that staying up too late for non-work essential tasks is damaging to your physical well-being.