If you have a stroller with you, then it would work ok, but otherwise I probably wouldn't want to carry it.
We bought a couple of big water bottles, with built in straws, and we found these worked really well. We would buy a couple of large drinks and share them out between the 3 of us, the large drinks are huge so there was plenty to share around, and also the bottles were sturdier than those paper cups so we could carry them around quite easily.
we also like to use the freezer to freeze half a bottle of water then top up with cold water in the morning, it stays nice and cold all day that way.
Bev