a piece of cake you cant eat
A piece of cake you can't eat is when someone says it's easy, but it ends up being the worst thing you ever tried.
You said this game was easy. I lost every round. You said you'd win. You got eliminated.
He said the test was a breeze. I got a zero. He said he'd help. He was on the phone.
She said the cake was amazing. It was inedible and full of hair.