Saw its function as to carry beverages. Later I found it works wonders for small talk too; to play drums; to workout when is full and to juggle with it when is empty; to hear the most funny ideas out of kids, —it's my other head, my pumpkin head—; and to hear interesting stories from old folks —in those days, in those far places...—. Got me a wax marker and now it works as well as an sketchbook and notepad. It helps to better understand some of the ideas of geometrical perspective that can be missed when drawing over flat surfaces.
It really shouldn't be such a curious item, as not so long ago these were used to be all around... I think you nostrichmen can realize by now why this happens... This be my ego talking but as I saw them looking at it, and then looking to see their bottle's at hand, they kind of realize they've been scammed.