I found a channel in youtube, named "Brett's diapers", saying it's developing "stretchy diapers" that can hold a lot, because they don't have padding and just grow grow to fit more and more pee.
However, I think this is fake. He's being "developing" this for 5 months, and every video looks exactly like the same "diaper". The wobbling of this thing looks like that one of a water balloon, and in the last video (in the shower) I think you can see how something looking like a ballon is contained in his boxers.
But there's also a video where he says he's peeing and the diaper is indeed feeling up, and his hands are away from the diaper.
Anyone has any guess on how does he do it?