Ask HN: What do you think about the team building activities

So we are a small start up of 10. Our boss is trying to push a Hackathon for a product we can potentially monetize as a team building activity. We did Marshmallow challenge last year as a team, and I thought it was the most wasteful mornings of my life. I think I agree with the person here: https://maskofreason.wordpress.com/2012/02/01/refuting-the-marshmallow-challenge/

What are your opinions about such activities? Do you folks do any?