If that's really hot chocolate, then there's something really wrong here. Or the place Michiru bought it at was just ripping people off. Thankfully it's just one drink, so it's not like it's a big enough deal for Haruka to throw a fuss about.

Especially not when there's something so much important right here. Michiru herself, of course. How could Haruka care about some awful-tasting drink when she can just instead focus all her attention on her very favourite thing in existence?

"It is, but you're kind of making me tempted to drink some more."

Because it's getting her little touches like the brush of that thumb and Michiru leaning against her, of course. It's mostly a joke, but don't think she wouldn't do it for real anyway if that's what it took.