There are so many fun duct tape patterns out now, you can pick a fun one that goes with your party theme. Just remove the original wrapper and replace with duct tape.
We went to a party this year for one of my son's classmates, a little girl, and they did the duct tape water bottles. Hers were Hello Kitty. They were really cute and then she had those flavored Kool Aid pour ins so the kids could pick which flavor they wanted their water to be. The kids really enjoyed that.