Any Toslink cable will work with the standard connections, not the Mini Toslink.

The Sonos optical adapter won’t work as that converts an optical signal to HDMI, which the Playbar does not have.

They are semi-rare, but you can get mini-TOSLink to TOSLink adapters, still. It’s been years and years since I needed one, but I think you can still get them from places like Amazon. Heh, like here. 

Why would OP need such an adapter?

In the past, some TVs were equipped with mini-TOSLink. Mostly Panasonic, I think, maybe Philips, too. It’s been years since they were made with them, but they’re still out there. I recall maybe 10 or 15 years ago needing to buy one, but I don’t remember why. It was before I worked for Sony, and that’s a long time ago.

Wow, I didn’t know mini-toslink was a thing until this thread. Thank you. https://en.wikipedia.org/wiki/TOSLINK

Some laptops and very few tablets also use mini-TOSLink.
Desktop PCs usually use normal-sized TOSLink.
And audio equipment in general is using TOSLink.

In general if you have stationary audio equipment it is recommended to use digital/optical connections as they avoid quality-loss which is common in all other kinds of physical connections.

I’d certainly recommend the ARC connection over the optical, when possible. Bandwidth is more limited across optical. Atmos can’t be carried for Sonos devices across optical, nor can the Sonos devices that require optical connections interpret the signal. 

I totally agree. Of course digital connections with a higher bandwidth like a HDMI supporting 1.4 and above (which includes ARC) are preferred over optical cables with a lesser bandwidth.

I am just saying, that optical is preferred over audio jacks, clamps, DIN connectors, RCA and also XLR connections if they are used for analog connections.

 

In this case, the OP has a PLAYBAR, which only has a standard TOSLink connector. We don’t know what the TV is.