I’m assuming you meant without running a 50 foot HDMI cable, and I’m afraid the answer is none. Sonos isn’t an effective solution for projectors at the rear of the room, they have no fully radio connected front speakers, and all of Sonos’ soundbars (the Ray, the Beam, or the Arc) are all designed to be hardwired in order to get the audio associated with the video. 

If you wanted to use that 50 foot HDMI cable (and I’ve not looked at lengths and signal drop off, you may need to look at some sort of signal booster midway), and depending which type of codec you wanted to have, you could get a splitter device that sends the signals to both the projector, and the Sonos, and place a switch of some kind (some of them include a switch) that would allow multiple devices to be connected. 

There is the HD Fury Arcana, the Feintech VAX04101k, and the OREI HDA-935. You can also order from those links from the companies directly, or check your local retailers for availability. Amazon may carry some, depending on location. At this point, there may be more manufacturers, I haven’t been keeping track.

I’m not a huge fan of Sonos for use with projectors, but many have made it work. 

Thanks Bruce, and yes i meant without. What about an optical cable or ethernet? 

What about them? I know an optical cable’s bandwidth restricts the signal to Dolby Digital, but I’ve also never needed to look at attenuation length, or ‘repeaters’ that might go in the middle.

I’ve never looked at internet baluns, other than the occasional mentions here in this forum (probably 3 or 4 times, not frequently). 

You may be better off speaking with an audio / video professional, rather than some random person on an internet forum. At least then you could go back and demand it be made right, since you paid for the system.