It's a situation he would normally be inclined to simply watch and see how it plays out-- a very specific delight in seeing Dorian, That Mage from the library, Tevene, suffering through a social situation from which he cannot exact himself. Perhaps he's feeling kind. Perhaps he's merely drunk, but he wanders over in the direction of Dorian and his companion.

Where Dorian has red wine, Thranduil has something white and sweet-- and he hasn't found anyone offering something more than that, so at least the question is genuine when he steps into place next to the woman, and asks: "Where, my friend, did you find that?" raising his own glass in demonstration.