Lots of food at the airport.

For breakfast, personally I like Ya Kun (depends on outlet as well). The toast is usually delish and the coffee nice and thick and bitter. Unfortunately, it is at T3, and I have never had it at that particular outlet.

There are Wang's Cafe or Toastbox at T2, or Killiney Kopitiam airside. I'm not a big fan or either, but they are decent and serve similar fare to Ya Kun. Traditional breakfast. If you want Laksa for breakfast, some of them serve it as well in the morning.