Co-Ed Sports Leagues: In the 2000s/2010s, this was a common thing for 20s/30s people to do. Kickball had a meteoric surge in popularity around the late 2000s/early 2010s. Almost all co-ed team sports have young adults. A good percentage of the participating population in co-ed sports is doing it because they are single and looking to date. However, there are some established couples/established teams who do things. It can be a bit cliquey and social circle to do. You're generally going to have a better experience in a sports league if you establish your own team from your existing circle of friends rather than sign up as a free agent to join teams that are 1-2 players short of a full team or a random team comprised of all free agents. This is even more true when the sport requires actual skill, like volleyball or soccer. Kickball is complete bullshiit and doesn't require actual skill. Regardless of the sport, most of the socializing and finding romance occurs after the end of the game at some sponsor bar. The games are filler for the actual picking up.
I recommend co-ed sports leagues if you're passionate about the sport. If you're doing it just for the dating, you're likely to be sorely disappointed. It's effectiveness is questionable and it's definitely not efficient. For efficiency's sake, you're likely better off going to fitness classes and doing approaches before or after classes, especially if you're joining leagues as a free agent and don't have social ties within the league. You're more likely to build social ties if you do the leagues season after season. Co-ed sports leagues are difficult to swoop into and get dates from random approaching after games.