My cat's obssession with Paper Cups

My cat Zoey is obssessed with these 3 oz. Paper cups I use to put my M&Ms in to eat. She likes it filled with water to drink out of. She even anticipates when I'm about to take one out for myself. I was in the kitchen this evening and she started whining at me. The only thing that would appease her is a paper cup filled with water. And now Toby has followed along with her and now I have two obssessed cats. I wasn't even planning on taking one out for myself this evening.