They open to everyone before night falls. 
I'll add Penny Black (Boat Quay), Wala Wala's (Holland Village),
Timbre (The Substation) and the Harry's chain (@ Changi Airport,
Boat Quay, Orchard Towers, Esplanade, etc) to those.
A small pub that you can literally freeze in is Eskibar (Circuit
Roat, Holland Village) - the freezer room's temperature is set at
-18.
Fluid (Far East Square) is not as crowded as the aforementioned
places can sometimes get.
