Sam had mostly gotten used to the moments when she was completely thrown for a loop when communicating for an angel, but Cas still managed to take her by surprise. She put her hands in the pockets of her hoodie and watched him, waiting a few moments for him to make a decision-- one which appeared to be very difficult for him to make-- and then started to wonder if he wasn't going to be able to make it at all.
"You have to go up to the counter," she informed him, "And tell the hologram behind it what you want."
It was still a weird system for her, and she couldn't really blame him for having difficulty with it. But on the other hand, she'd have expected his hunger, however novel it was to him, to have a bit more of a driving effect on him. Maybe that concept was learned rather than instinctive; the nerdier part of her mind was slightly fascinated by that thought, but she was more concerned for her friend than anything else. Apparently, he might need some hand-holding (not literally, she hoped) through the process of figuring out how to be a human. "Do you know what you want?"