During the evenings go a bit further to Robertson Quay or even further up the river from there. CQ is very touristy whereas RQ is more of an expat place - more beer and sports shown live and less loud music and wasted tourists. The bridge at CQ is a great place to drink though, there should be loads of people there every evening as long as it's dry out.

CBD and Bugis you can skip after ticking them off your list. If you're on Orchard in the evening then check out Emerald Hill for some drinks.

A good place for beers in the evenings is Chinatown, especially if you head to that big HDB complex with a beer hall on level 2. That's how the locals drink.