There is catering on some local Intercity trains as well. It used to be served using small trolleys, but a few years ago they switched to backpacks and added more brands like Starbucks.
The NS is not providing structured information about where they are.
"On Intercity's throughout the Netherlands and on the NS Hispeed train ..."
Source (Dutch)
However, you'll have most changethe greatest chance to find them on the longer IC tracks, e.g.:
- Utrecht ⇄ Zwolle
- Zwolle ⇄ Almere
- Utrecht ⇄ Den Bosch
- Utrecht ⇄ Deventer
- Zwolle ⇄ Groningen
There is some info about this on Wikipedia, but I'm not sure how acurate it is.