we have a similar cup from boots with a curvy plastic top which stops utterly nothing spilling whilst in transit, I've taken to jamming it amongst things under the pram. Granpaw took Boomer out in her pram recently and I had explained about the cup, he smugly jammed in into a plastic container of soft play cube things and headed off. Neadless to say he returned with an empty cup and wet cubes (that sounds a bit unfortunate!)