I just wanted to make the point that waiting for someone to return from a break before talking to them can be considered polite, instead of an impolite ambush as indicated in the previous comment. Of course, there is no one-size-fits-it-all solution.

There is - schedule a meeting (even if it is a 15 min "sync") the day before, so I know I have a context switch coming up.

In my experience, that is not an acceptable solution for everyone. I have worked with people who despise these kinds of scheduled short meeting, because "we are sitting in the same office and can always talk to each other".

That having said, my personal preference is also the scheduled 15 minute meeting.