As Jacob_M mentioned, the "lounge" is really a cafe open to all, after passport control and near the flight boarding area.
When you check-in, ask for a voucher: valid for one drink and one sandwich (last time they were pretty strict on this). They don't always volunteer the voucher, and may think you need to be Senator too.
Not very comfortable and not worth coming early for. Best to do the fax check-in and check in late. Not sure if the "lounge" is open if you are on the middle of the night Munich flight.