a piece of cake - Something so easy, you could do it while eating a burger and

Something so easy, you could do it while eating a burger and still have time to laugh at your friend’s jokes.

That test was a piece of cake. I did it in my sleep and still had time to eat.

That quiz was a piece of cake. I finished it before my coffee even got hot.

This assignment was a piece of cake. I did it in five minutes and still had time to text my crush.