General:
* Break
* Pause
* Interval
* Respite
* Digression
* Intermission
More specific:
* Diversion (if it's a brief change of activity)
* Episode (if it's a distinct part of a longer event)
* Passage (if it's a brief period of time)
* Incursion (if it's a temporary interruption)
* Sojourn (if it's a temporary stay)
The best synonym for "interlude" will depend on the specific context of your sentence.