Yes, also rental cars and camper vans need a valid Swiss motorway vignette. Usually Swiss rentals do have a valid vignette arranged by the rental company, foreign renting companies most likely do not.
In order to avoid a heavy fine we suggest to make sure with the rental company that upfront that the car has a valid Swiss motorway vignette.
Any vehicles and trailers over 3.5 tonnes are subject to the LSVA / PSVA.
Related articles:
What happens if I drive without a Swiss vignette?
How long is the Swiss motorway vignette valid?
Are shorter term Swiss motorway vignettes available (daily/weekly/monthy)?