You can stay on top of Marina Bay Sands - these rooftop areas on the 55th floor close at 4AM and then use the remaining time outside MBS/Marina Bay.

As far as of 'couple drinks' - make sure that you have an adequate budget for the rooftop bar at MBS - the cheapest drinks start from $30.

Several years ago I wrote here on a thread 'what to do in Singapore if you have 24h' - you might find that useful.