The CW has put together a Superhero Fight Club 2.0 video that includes The Flash, Green Arrow, Firestorm, The Atom, White Canary and Supergirl. It also has Felicity Smoak, Cisco Ramon, John Diggle and J'onn J'onzz. But if you want to see it, you have to download the CW App on a mobile device (because I'm sure there are no unauthorized copies on Youtube).
The original Superhero Fight Club put the heroes and villains from the two series (Legends of Tomorrow hadn't started yet) into a steel cage match where they fought one-on-one. This new one removes the villains (accept for a surprise ending) and puts them in a 'danger room' setting created by Cisco and Felicity. It also includes Diggle seeing an alien for the first time…
The teaser below gives you an idea of what's going on.