'Efficient' is the term, give him that. Illumi only looks at Hisoka - the visual equivalent of a shrug - and oh, they're already leaving this store. So no shoes? And no flashy golden tie, but that's fine by him. He spots Hisoka's chosen distraction before they make their way up to the counter, but his only comment is-

"Ah, well, I don't have to try very hard," which has nothing to do with smoothies and everything to do with dressing like a boring old person. He says try very hard and means sticking himself full of needles to look more ordinary, of course— for more difficult jobs he's needed to, but this one happens to be so basic there's no point in any effort beyond the bland outfit. "So yes, that's right. I'm hardly showing up to entertain these people."

The cashier girl- bless her heart- only then seems to blink herself out of her episode over Hisoka when Illumi plunks his elbow on the counter and stares past her to the menu. She gives him a look like she's half panicked that she was staring so blatantly at one of them and now there's this other one and- and what exactly is with that thousand-yard stare-? While Illumi pays no mind and simply points at a picture- "Strawberry for me."