How to clean system data?

There is no function that can clear System Data.

System Data are cache files from apps, which are used to provide the best experience when using iOS, and ensure that apps open faster and there are minimal loading times. When your iPhone "fills up" over time, the System Data will automatically be cleaned up to make room for new data. You may also find that the amount of System Data shrinks after a software update. But it is not necessary to clean up that part, since iOS itself manages what is to be used and what is to be thrown away.