I don't know how Sam would spin it to get Dean to go, but I'm pretty sure the drive back would be a fierce debate, with Sam taking the position of devil's advocate just because "It's art!", but secretly agreeing with Dean the whole time. At some point on the drive back they stop for milkshakes and fries, and while Sam's sitting there, watching the condensation run down the side of his cup, with Dean still muttering about how stupid the movie was, he gives in and starts laughing because it really, really was.
And he's slightly drunk from the relief of having a normal day with Dean, no sign of the MoC except that Dean's sleeve is rolled lower than he used to wear it, and it's probably a slight attack of hysterics, but seriously: a mime who's secretly a cockroach.
And Dean falls silent, studies at Sam a little worriedly, and sticks him in the back seat for the rest of the drive back, because obviously he's too tired to function anymore and he always gets a really bad crick in his neck when he falls asleep in the passenger seat. He gets a crick in his back instead, and both his knees lock up on him when they get back to the bunker and Dean chivvies him out of the car, but it's the thought that counts.
In the morning Dean makes French toast with the last of the eggs and the stale back end of a loaf of bread--there's not enough egg mix and it's a little heavy on the spices, but it still tastes better than anything Sam's had in years.
(Two weeks later, on their way home from a job, Dean pulls in at an art house theater. Sam's been dozing for the last hour, so it takes him a minute to realize they're not at any of the kinds of places they usually stop, and then another to realize Dean didn't make a wrong turn.
"What're we doing here?" he asks, trying and failing to stifle a yawn.
"Saw the sign for Flash Gordon and figured you owed me one," Dean replies; the undercurrent of glee would be worrisome if Sam was functioning well enough to notice. "And I feel like having some kettle corn."
"One what?" But Sam gets out of the car even as he finishes asking the question. If nothing else, it gives him the chance to stretch.
"One stupid movie, that's what. Still can't believe you made me watch the thing with the cockroach dude."
"Not like I dragged you," Sam protests, but it's pro forma, laughter bubbling against the back of his throat, because a Dean who's bitching about pretentious foreign films is better than almost any other variety. "And I thought you always complained about the hulls getting stuck in your teeth."
"Sometimes you gotta live a little," Dean declaims airily, but there's a smile tucked into the corner of his mouth as he drags Sam inside.
He spends the rest of the trip back exclaiming "Gordon's alive?!" at random intervals, and for a few hours it's like they're teenagers again, just them and the car and the endless, open road.)