We tried doing this, in many different forms, but it never worked out. At first meeting, almost everyone is present, the second one a half of the team, the third one practically nobody. No matter what we do - eat food, drink tea, play games, tech talks... Nothing works.

Small groups worked only if the people already have a relationship (which is rare), I never successfully got people to consistently join small groups with people they didn't know.

During the office times, this just happened naturally as people felt like it. I don't think you can schedule fun.