Guys, Do you ever drink out of the same cup as another girl?

I was hanging out with this one guy I like tonight and some friends, I went to Starbucks and got a coffee, and I had already sipped on it and my lipstick was on the cup - that didn't deter him, and he would drink out of my cup every so often, so we were basically sharing the drink. He has done this before at work as well. Do you guys do this normally, and if so is it generally with girls you have interest in?
Guys, Do you ever drink out of the same cup as another girl?
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