There is not a GI-Feature "Friendly Cup".
So you have to organize it by your own. Get teams for your cup by advertising in the right forum and set up a game plan. All teams have to challenge the team he has to play against.

Either you set up groups and every team plays against every other team in his group and the best go to the playoffs for the final. Or you play it like the "normal" cup from the beginning: every team that loses is out.