For such a short layover at such an ungodly hour, there's no point leaving the airport. If you already have your return boarding pass, then I'd recommend that you just remain airside and see what food options are open. I think the T3 food street is your best bet - and I think there are a few other local food stalls scattered around the airport that are open 24 hours.
Originally Posted by
spainflyer
Over at the "Food Street at Terminal 3" string the opinion seems to be:
Departed SIN Nov 17, looked at T3 food street and went directly back to T1 canteen.
T1 canteen is the staff canteen (restaurant for non-Brits / non-Singaporeans)
The T1 staff canteen (not a restaurant, but rather, a basic food court) is closed during his time of transit, not to say that the food over there is any great either. I personally prefer the Kopitiam food court at the basement of T3, landside (mainly for its variety).