How do you say when play that sport in German?

The German translation of "when do you play that sport?" depends slightly on the context and level of formality. Here are a few options:

* Wann spielst du diesen Sport? (Informal, singular "you") This is the most common and straightforward way to ask.

* Wann spielt ihr diesen Sport? (Informal, plural "you")

* Wann spielen Sie diesen Sport? (Formal, singular or plural "you") This uses the formal "Sie."

* Wann treibst du diesen Sport? (Informal, singular "you") This uses "treiben," which is a more general term for "doing" or "pursuing" a sport, and is sometimes preferred over "spielen" (to play).

* Wann treibt ihr diesen Sport? (Informal, plural "you")

* Wann treiben Sie diesen Sport? (Formal, singular or plural "you")

The best option depends on who you're talking to. For most situations with friends or family, `Wann spielst du diesen Sport?` or `Wann treibst du diesen Sport?` would be appropriate. For someone older or in a more formal setting, use the "Sie" forms.