Aside from the changing pint glass color and level, the Sky set top box / decoder, will also overlay the subscription ID at random intervals and locations.

I don't know if Sky does it, but Foxtel in Australia, in addition to the pint glass watermark, have a separate set of channels for public venues, which have different ad breaks/content to residential subscriptions. (https://www.foxtelmedia.com.au/foxtel-media-network/fox-venu...)