"Bathroom, I guess," he answers, a bit more softly than he was speaking a moment ago. "Thanks."

And then, as Sherlock is about to leave the room, he speaks up, though still softly. "Hey, Sherlock. How about we try not to get too cutesy in front of you, and you refrain from commenting on or giving advice about our love life. Sound fair?" he asks, though he says it kindly, not confrontational. That's just some boundary setting he needs to do, while offering up a boundary for Sherlock as well.