Ask HN: What makes a GREAT hackathon?

I'm helping organize the next hackathon where I work. We have something like 30-50 people participating across technical frontend and backend teams, including UIUX folks, PMs and others.

Typically our hackathons are 3 days long and are self-organized in to teams who go for various bounties. Anyone can suggest a bounty which might come with a trophy and maybe a gift card. Typically - but not exclusively - the hacks have been work related. We usually have a food challenge too during the event. Last time it was "who could eat the most pirogies" (the winner ate 100 over 3 days :-) ). We have a show & tell event at the end and open voting on the winners.

We're open to changing things up!

What have you seen (timing, tasks, organizationally or anything else) that works well or poorly in a hackathon?

Thanks HN!