eat sb for breakfast

If you eat something for breakfast, you can do it effortlessly, and if you eat someone for breakfast, you can beat them easily.

如果你eat something for breakfast，那么就是说你可以毫不费力地做到，如果你eat someone for breakfast，那么就是说你可以轻松击败他们。

不费吹灰之力制服(或打败)

He eats people like you for breakfast.

像你这样的人，他不费吹灰之力就给制服帖了。