朝飯前だ。
It is a piece of cake.
朝ご飯よ!
そんなの朝飯前だよ。
That's a piece of pie.
そんなの朝飯前だよ。
そんなの朝飯前だよ。
Doing that will be a piece of cake.
Nothing could be easier.
It's as easy as pie.
It is breakfast time soon.
It's time for breakfast.
(直訳すれば)It is a before-breakfast job―(意訳すれば)―It is an easy task―(英語風に言えば)―I make nothing of it―I make short work of it―I can do it any day.
It's a snap once you get the hang of it.