I’ve seen a few questions here about how to stream MLB audio from the At Bat app to Sonos.  I recall that a few years ago there used to be an Air Play icon right in the app that you could use to easily stream to Sonos.  But that no longer exists in the MLB app.  

So here is how you can do it in 2021.

1. Open the app on your phone and start playing audio for a game
2. Swipe up on your iPhone, this brings up the Control Center
3. The Control Center should show a section that displays the currently playing audio
4. From this section you will see an Air Play icon
5. Click on Air Play and you should see your Sonos as an option (as long as it is a somewhat modern Sonos that supports Air Play)