need good cleaning product for the plastic back window

[Norminhouston]

Plexus is a good product for that purpose.

[Perfectlap]

PLexus is also good for the windscreen and your headlights. Basically anything made of plastic. I use it on my helmets, bought a case of it.
For deep cleaning and swirl removal of the plastic try Renovo from openroadmotoring.com (they also sell 1z leather which is the best cleaner I've used)