Why do Docs, Sheets and Slides keep recreating their data?
You shoud disable those apps:


Go to Settings › Apps – where you usually deleted the data
before deleting data:


push the "force close" button to make sure the app is not running. Else it might recreate data before you reach the point of disabling it.
then push the "disable" button, so it won't start anymore.
on "disable" you might be asked if you wish to revert to the "factory version". Say yes: this will remove all updates the app has received, and which are stored in "user space" as well. So this will even free additional space

finally push "clear cache" and "delete data", to complete the cleanup job.


Now that it's disabled, it won't start on its own anymore – and thus not collect or recreate any data. Nor should any updater pull updates for it.