While I was at the charter school, we held a celebration of learning twice a year. It was a culminating event where the students could show off their projects they had been working on all term. It was exhausting for the teachers and required long hours, but in the end the students were held accountable for their work. Their projects would be displayed along with everyone else and many of the students worked hard, knowing it would be in front of a real audience.
It was much more fun than a packet of worksheets or a test. It was a bonus if we made the projects meaningful in some way to the students. If they had an authentic audience, then they had a purpose and were generally more motivated.