This is not an easy physical task. I'm talking about for those sweatshirts that have an unsecured thick "shoelace" style string as the controller for how tight the hood is. If you unknot and pull it too far, the soft end of the string will go in too far. You can't cut things open nor fully reinstall - you have to kind of wiggle it out. Note that you're also not allowed to put a finger or any tool into the hole. You have to use the stretchiness of the fabric, plus friction, to gradually get it out.

It will have to be done by an autonomous robot hand or similar, no direct human guidance. (it can have been trained any way you like before that)

aka "pulling a hoodie string back in"