Help needed to ID source of a scene

[KneadToKnow]

I think it's a scene from a movie, but it could be from a TV show or possibly an extremely vividly-written book. I remember it as a story someone is telling about someone else, and the clearest thing about it I recall is the description of someone using the same toothbrush he used to clean his teeth to then clean his watch.

I know that's not much to go on.