C3PO had one demand: make sure I have a straw hole inside of my mask. It's just supposed to be a costume, not a torture device, so I hope they not only had a straw hole but they also had a pee and poo hole. I'm not saying that's the best way to use the restroom, but it's better than holding it in when you really have to go. Just hose the costume down at the end of the day and you're fine.
This reminds me of when I played Santa and delivered presents to sick kids. I had to wear a glued on beard which didn't allow me to drink anything. We didn't have any straws on hand so I just slowly died as the night went on. This was a California Christmas, so it's not like it was cold. I think it was still about eighty degrees.