He opens his mouth to say he doesn't want a drink at ALL, but of course now that he's thinking about it, he realises that he is indeed somewhat thirsty.

...He definitely doesn't want this particular, sugary disaster however, so after a quick glance around he foists it on a passing child.

"Here. No need to thank me. Now go away."

He turns away from the (understandably confused) child and turns back to face Hythlodaeus, scowling. "Cold mint tea, no sugar."