Instead of going to the top of Marina Bay Sands I’d go to the top of the UBS building at Boat Quay up to the top and 1-altitude bar (or do both). Its the highest bar in Singapore (and maybe the highest view), you’ll be looking down on Marina Bay Sands and you get a full 360 degree view. You can’t access the infinity pool at MBS anyway unless you’re a resident.
I also like Level 33 which is a micro brewery on the 33rd floor of a building in the business district. Really good beer and the food is pretty decent too.
I like Club street also, old colonial style buildings tucked in between the business district and China Town. Lots of decent bars, roof top terrace bars and coffee shops…really lively on Friday and Saturday nights.
I prefer Boat Quay to Clarke Quay, the latter being really commercialised and glitzy (Hooters etc), Boat Quay is a bit older and less glitzy, but they’re walking distance between the two so can easily do both. In fact I used to meet up with people at Clarke Quay for an early drink, walk unto Robertsons Quay for a bite to eat (really good Korean restaurant there amongst others, also good if there are any sporting events on you might want to catch) then wander down to Boat Quay after.