Water You Making?

I work at a coffee shop and our cups for cold drinks are clear. A customer makes an online order, so I prepare it and have it ready to hand off when he arrives at the store. Another customer comes in and orders two cups of water. I make the drinks and hand them to her at our handoff plane, and then I get the mobile order ready to hand off as that customer has arrived.

Customer: “What was that drink you just made?”

Me: *Confused pause* “Water?”