Your user manual should have some information about the best cleaners to use for sanitizing your system, but you could contact the seller directly for clarification. I would strongly recommend that you don’t simply use one of the household cleaners you have in your cleaning cupboard.
My advice would be to either purchase a specially designed RO sanitizing solution or make your own out of white vinegar and water. You need to sanitize the system without contaminating it with something that may linger in the system even after flushing it several times.