They could actually hold basketball games, if the NBA would get on it. Teams would have to be in tight quarantine, with delivered sterilized food, etc. for a few weeks. Then everybody gets PCR and antibody tested. If all goes well, the teams could play games in empty courts and televise them. As the only sports on TV, the audiences would be HUGE!

This is inspired from all the quarantined couples making amateur porn and selling subscriptions online. As long as your quarantine is tight, you should be able to interact with other people in tight quarantines. Hardly anybody really has tight quarantines, but they are not impossible.

I would start with basketball, because the teams are so small. But they could do this with most sports.