Disable Offline File Sync with Group Policy

You can disable offline files using Group Policy. Computer Config\Admin Templates\Network\Offline Files

Allow or disallow use of offline files feature: Disabled
Prohibit user config: Enabled
Sync all offline files when logging on: Disabled
Sync all offline files before logging off: Disabled
Sync offline files before suspend: Disabled
Remove ‘Make offline’: Enabled
Prevent use of Offline Files folder: Enabled