Nightclubs in GTA Online are businesses included in the game as a part of the After Hours update. Any of the ten clubs can be purchased at the Maze Bank Foreclosures website.
One of the simplest options is the gang attack in Mount Chiliad dirt road tunnel. It’s available from 20:00 to 04:00 and there are only 15 bikers in it. All of them can be eliminated by the player from a safe distance using a sniper rifle.