Hmm. 9S hadn't liked the wine at the Prince's ball, but that could just be because it was the Prince's. But more importantly...

"Why don't you try some?" You know, just so 9S' curiosity is satisfied. "You can drink, right? You have a human shape and everything, so..."

It's hard not to have his thoughts linger on 2B and how they could've been together at the Carnival -- that night at the ball... he'd been torn between anguish and joy -- so he's eager to latch on to something else.