As for all rental accommodation, it depends on the contract you have with the company you rent from.
Look for the rules for your owner they should be in your contract but might also be online if the owner is up to date, if you can not find them you can go by general rules.
No links as this is what I was brought up with.
For a short rental:
If nothing was said in the paperwork you empty the trash, make sure all dishes are washed and leave the caravan in a general tidy way, without going far out of your way to clean the whole caravan, wiping the counters and such should be done in my view.
If your paperwork indicates you have to pay a cleaning fee, you should still leave it in a proper condition but wiping surfaces and cleaning the toilet before leaving should not be needed.
On the other hand, if you have denied paying a cleaning fee and will clean the caravan before returning, it should be clean enough that you can eat from every surface, and leave everything as clean as possible with water and cleaning liquids.
For a long term rental:
The same rules apply as for a long term rental of a furnished house.
In my view that means that you clean the caravan well a few days before leaving and you do the dishes, take out the trash, clean the bathroom and vacuum the floor on the last day.
The rental company and/or the new tenant will want to do a clean before the new tenant moves in, but it should not be hard for them to do it.
Of course, if the carpets are due replacement or the plates are worn out, you should contact the owner and take his guidance.