Around the 11:50 mark, when they’re waiting in the bar for Cupid, Dean dresses his burger, but gives up before eating it and pushes his plate away.
“Wait a minute,” says Sam. “You’re not hungry.”
Dean hesitates just a moment before answering.
“No,” he says, as he looks directly at Cas.
Only then does he look back to see if Sam bought what he’s just said. “What? I’m not hungry.”