John looks up from the pot of water he's currently set to boil. It's a much quicker process than anything they have at home, and it's a stranger construct, but the idea is essentially the same.

He'll hand Sherlock tea, though, because that much he'd already had prepared. "That doesn't surprise me at all, the way you've been going at it. Are you having fun?"

He's actually kind of honestly asking, not being sarcastic.

"Fair warning - the milk tastes a bit off. I think it may be soy."