out of a paper bag
(one's) way out of a paper bag
A phrase use emphasize that one is particularly dim-witted, unintelligent, incompetent, or unable to do something basic, simple, or straightforward. Jeff's new boyfriend sure says some dumb things. The dude probably couldn't find his way out of a paper bag. Don't assign that project to her, she couldn't punch her way out of a paper bag!
someone couldn't — their way out of a paper baga person is completely unable to do something, either through ineptitude or weakness. informal
1999 Time Out N.Y. The problem is, he also, at the time, loved Victoria Tennant , and she can't act her way out of a paper bag even if you soak it with a hose first.