What do people do at hackathons?
normally they build teams and spend some sleepless night working on one project. The aim of the hackathon is to develop a minimum viable product (MVP) to present it to the audience.
As hackathons usually take place on weekends, it is impossible to build a completely functioning app. But it is important to make a high level presentation of your product - that helps to emphasize the strong size of your app and to pay less attention to the weak ones.
Except development, hackathon is the event for communication, experience exchange and having fun. And these three components are mostly more important than the product success and prize winning.