At logoff, delete local copy of users offline files
Computer Configuration\Administrative Templates\Network\Offline Files
Deletes local copies of the user's offline files when the user logs off.
This policy specifies that automatically and manually cached offline files are retained only while the user is logged on to the computer. When the user logs off, the system deletes all local copies of offline files.
If you disable this policy or do not configure it, automatically and manually cached copies are retained on the user's computer for later offline use.
Files are not synchronized before they are deleted. Any changes to local files since the last synchronization are lost.