Don't get caught up in "interesting" and "unique". There are lots of fads that come and go in the fitness industry but the simple fundamentals stand the test of time.
Assess their needs. Aerobic, anaerobic, maybe both?
Train those systems accordingly. For rugby I'd assume they need to be able to move constantly with sprinting bouts mixed in with jogging.
I'd program high intensity intervals. Sprint/walk. Sprint/jog. Use a variety of drills that include starting, stopping, cutting, even fighting through resistance as when getting tackled.
Increase the duration of the training sessions to match the longest stretch they'd be playing.
They're athletes. They don't need to be entertained. They need to be prepared.
As a test you could design a shuttle run for time. Rest and repeat to test their ability to recover. Timed sprints have a way of bringing out the appropriate effort. Miss the time and face the consequences.