You can sleep inside the sportscentre with your own airmatress and sleeping bag. The committee will indicate where you can place your stuff and where you can sleep.
Alternatively you can sign up for a cabin (Blokhut). Those are wooden cabins with two floors, where there is space for 15 people in total. You will most likely end up sharing this cabin with some other teams. It costs 17.50 euro's per day per person, and a deposit of 150 euro's per team is asked to sleep in the cabins.
Of course there is also always the option to sleep in a nearby hotel. But this has to be arranged by the team itself.