Okay...I had to post this story.
When I was 20 I lived with my close friend, also 20. One weekend we had a bunch of friends staying with us, and her back went out. She was in a LOT of pain and her stepfather had to drive across town to get pain medicine, so her mother gave her some codeine, which was all she had on hand. The codeine made my friend totally loopy. She was so weak from the back pain that she couldn't lift her head or hand, so she asked one of the guys to go in the kitchen and get her a sippy cup. I walked into the kitchen to find him messing around.
Me: What are you looking for?
Him: A sippy cup.
Me: We don't HAVE any sippy cups.
But, what an idea! So I drove to the store and bought 3 sippy cups and a bottle--enough so that everyone could have one. My friend was so happy, she was still loopy from the codeine going, "Oh I love you, you're so wonderful for bringing me a sippy cup...look, it's mice dancing with cheese! I want to dance with cheese! Can I dance with cheese?" (referring to the design on the outside of the cup)
The next week, after she was better, she said, "You would be the coolest person if you would take one of those to work with you."
So I did. I got a few stares, but nothing really bad. I still do use them/take them to work with me sometimes, and they worked really well when I was down with bronchitis because I didn't have to worry that my cat would jump on the bedside table and knock them off.
I have a male friend in his 40s who drinks out of them at work too. But he has two little girls and is very absentminded so it could be that he didn't notice what he was grabbing on the way out.
so that's all I have to say, sippy cups are cool and fun sometimes. And SOMEWHERE on the Internet I believe there is floating around a picture of me drinking out of a baby bottle. (my friend and I look a lot alike so she had to convince people it was me not her and no it wasn't a fetish)