I was never into hackathons. Usually something organized by a company and prizes awarded for something that managers without any Computer Science background or otherwise merit reward.
I am only judging the ones I was offered to send in teams but always refused. They appeared to be a rip off and and let's call it as it is: shit show.
I don't think that a hackathon solves anything worthwhile. If it would, why not make everything a hackathon? Why don't declare the exception the rule?
Good stuff takes effort and time. Crunch mode or death march as I used to call it because with their pale faces after three weeks without any free time, was generally something I despised and prevented in the first place.
I build the only successful Web Application in Financial Systems in a global bank and I knew we need to think smarter with all the responsibility and accountability. So we always sharpened our axe first.
I let my best devs work as much and long as they wanted because if you are in the zone, you exploit it. And yes, quite many freely worked at home on weekends as well, but I pushed them hard to not put this into the normal work stream in order to prevent any fake improvements that come to hurt them.
I gave them the promise to any free time they wanted and when they wanted given that they take care of their absence beforehand. I was never disappointed and people work differently. One guy worked month on no end, and suddenly hit me 9 pm "Boss, I need a break, give me two weeks starting tomorrow." Always granted without any hesitation.
Sprints? 80%, not 120% masked as "challenge". No dev gets bored. They need the feeling of being free to do their craft.
It worked best.
That's why I never personally as well as with any of my teams took part ever in a hackathon.