Small-sided games are at the heart of modern coaching theory. It promotes rapid decision making, gets them many touches on the ball, and asks players to solve problems they’re likely to encounter in real games. This was a great article from World Class Coaching that is worth a read.
Note the variety of goal (quantity/location/position), objectives, and player makeup. Leveraging the variety you can introduce in such a limited space, with some creativity there really shouldn’t be many game scenarios you can’t replicate.