Many years ago (30?), when REALLY large fountain drinks started popping up at the convenience stores, the container was made like a milk carton, complete with fold on the top, but was cylindrical at the bottom. A small clip held the top closed, but it could be opened if needed to pour multiple drinks.
My main memory about that short-lived container is that the soda went flat pretty quickly. You’d probably be hard-pressed to even find an image on Google for it.