Convertible Cup

So, if you recall, Nathan got a convertible Mustang (Power Wheels version) for his birthday back in November. Since then, he's always identifying fellow convertible vehicles around town. Not too long ago I was getting our drinks ready for supper when Nathan asked for a "convertible cup" for his juice. When I asked him what he meant, he explained that he wanted "a cup without a lid". Of course! What was I thinking?!