On my journey to Edinburgh a couple of weeks ago, the staff came round with the cold drinks and I asked if I could have two. (It was late morning and very few people were drinking alcohol.)
The host said, "If I have any left when I come back after serving everyone, I will drop you one off". I replied "Don't forget" and smiled. When he passed back, nothing, although the cart was still well stocked.
No big deal, I will walk up to Coach G (not very elegantly) and buy a couple of cans. The cans sold are larger than the complmentary ones. Anyway with the carrier bag and the cans on my table it was clear I had been to the cafe bar and bought the two cans.
The outcome was that between Newcastle and Berwick a can was dropped off without asking for one, so I saved that for my nightcap.