Unfortunately no Joerg
I was there in February and the way I managed was to drink instant for the first week <ugh!>. That way the Starbucks I had there in the second week didnt taste too bad. In other words I was forced to lower my standards. I went to a p-lace called Clark Quay where there was a couple of streets with an international themeMIGHT have a place that serves drinkable coffee.
You could also try one of the 6 star hotels there - have a high tea. They may serve a decent coffee but it might cost you $10 or more. My wife and I went to the Fullerton which is the old GPO refurbished. Worth a visit anyway.