Building "Play" into long endurance training rides

Hello all, I’ve been reading Hidden Potential by Adam Grant. It’s a really good book with a lot of application to coaching and training.
One of the key philosophy elements in the book building in play to training.
I’ve been thinking about how to build play into the long endurance rides on the trainer this winter. I’ve created a couple of workouts, but those aren’t really play.
How could we add play and fun into the long indoor trainer rides? What are your thoughts?