There's only 72 units in my detached condo sub and we're surrounded by houses and other condos so putting out notices isn't sound advice........
A spray bottle by the back door? If you get woken up, grab the bottle, spritz the cat a few times... maybe it’ll go off and bug someone else for a while.
Fair enough, and I understand your frustration with the nighttime goings-on. But please don't just snatch the cat up and dump him somewhere. That would be cruel, and not the act of someone who has a heart for critters.
I don't know the best way to find the owners, but there has to be one. They're irresponsible and stupid, and they should be advised of that fact.