Try some rules like the ones attached.
I haven't tested with Google Drive specifically, but it should work.
Basically, uses Application Control to isolate Google Drive traffic, and blocks the POST command to it.
Thank you for your reply.
Unfortunately this doesn't work for me, nothing changes if I apply this rule.
A prequisite for this to work would be that you have SSL scanning enabled. Do you have SSL scanning turned on?
I have spent quite some time trying to acomplish this scenario. It looks like MWG only recognises application name Google Drive if used to allow/block access to it. When application name is used with another criteria (Command.Name=POST) the Application name always seems to be empty. I managed to block uploads to Google Drive by blocking POST commands to URL *google.com/upload/drive*.
Please post if you have better solution.