Eponine wouldn't know underdressed if it danced in front of her, so she doesn't at what the man's wearing. More to the point, she doesn't notice. Her eyes are on the food, and her face lights up when she realises it's for her.

"Really, Sir?" she asks. "If it ain't too much trouble?"
But she snatches them anyway, because she's hungry, as usual.
The food smells delicious but it's the drink that catches her attention. She peers into the cup, looking at the bubbles. They tickle her nose, and she looks in astonishment at the cup.

"What is it?" she asks, doubtfully.