I’m not overly familiar with the Audi interface, but my understanding was that the Audi used Sonos speakers, and not a Sonos controller, so you wouldn’t be able to connect the two. 

However, if you’re using AirPlay 2, you should be able to send the same AirPlay 2 signal to either, when you’re in range of the respective networks. 

Do you mean my Audi MMI is able to manage AirPlay 2 signal from my iPhone?

You’d need to check with Audi. Again, I don’t know what interface they’re using. It could be just Bluetooth, rather than AirPlay 2. My Tesla works on Bluetooth, not AirPlay 2. I can use either AirPlay 2 to my Sonos system, or Bluetooth, when I’ve got my Roam up and running.

The Audi should also do wireless Android Auto or Apple Carplay. You’d command Spotify etc. directly from your car’s screen.