Beach 38° is basically an old industrial complex near Ostbahnhof filled with sand, heaters and beach volleyball nets.
It’s really a lot of fun and playing there when it’s cold and raining outside this is like entering another world. While around € 40 per hour might sound like a lot, it’s not that bad since you’ll be dividing this by at least four. The atmosphere is nice and relaxed, balls can be rented on site if needed. Plus, there’s some decent food and drinks at the “beach” to relax afterwards – if you don’t want to stay, you can just as well head over to nearby O Castelo for some Portuguese treats.
For those who are into climbing, there’s a boulder hall next door that I haven’t been to yet, since I am a lot more into sports involving a ball.
Hint: If you can’t get a reservation because all courts are booked, try Roberto Beach in Aschheim next to the Wakeboard lift (Erding-bound S2). It’s more remote and I think a little pricier but still a good alternative to not playing at all.