This is a funny scenario.
In the Manifest.Permission documentation
public static final String CLEAR_APP_CACHE
Added in API level 1 Allows an application to clear the caches of all
installed applications on the device.
Constant Value: "android.permission.CLEAR_APP_CACHE"
So you can get the permission to clear cache of all application. But I don't think there is any method in the SDK to use this permission. So you can just hold the permission and do nothing with it. Strange from google.
EDIT : This google discussion might be of interest. Dianne Hackborn specifically says that the above permission shouldn't be present in the SDK, since the API to use it is not there.