Spoilers: None, just general knowledge of the show.
A/N: I swear, I am not a Wincest shipper. But this got in my head and would not let go.
"Fucking Arizona, man," Dean griped, wiping the sweat off the back of his neck irritatedly.
"You said that about Texas too, you know," Sam said with a smirk, setting the gas pump back in its holder as Dean opened the passenger side door and slid in, shuffling down in the worn leather to rest his head back on the seat with a sigh.
"Yeah, well, it wasn't my idea to travel the southern border in July, either," Dean reminded him as Sam folded his huge frame into the driver's seat.
"Dude, it's the fastest route," Sam replied, turning the key in the ignition and shifting the Impala into gear.
"Yeah, well, it's a stupid route," Dean bitched, shuffling around uncomfortably as his sweat-damp shirt and the leather seat stuck to him.
"God, you are such high maintenance," Sam mumbled, pulling the car out onto the road, and Dean didn't even bother to open his eyes as he flung his arm across the seat to smack his brother's side.
"Shut up. Bitch."
Dean snorted, turning his face toward the open window and letting the wind cool his damp face.
They drove few minutes in silence, the sound of the road and the rumble of the engine the only noise.
It wasn't too long before Sam got bored, clicking on the radio and turning the volume down before switching to AM and sliding to the nearest news station.
"Ah hell no," Dean said immediately, "Change that crap."
"It's just the news, Dean. And you're supposed to be asleep anyway; you just drove for ten hours."
"Exactly, I'm tired and I don't want their stupid voices droning at me, I won't be able to sleep. Put a tape in."
"Oh, and Metallica will help you sleep?" Sam scoffed.
"Of course," Dean said sternly, sitting up and opening up the glove compartment to grab the cassette, "Enter Sandman, dude."
"Dean, no, come on," Sam bitched, putting his whole, stupidly big hand across the radio to keep Dean from putting the tape in.
"Don't be a bitch, Sam," Dean growled, "move it."
"Dean!" Sam squawked, trying to elbow his brother in the ribs as Dean grabbed his wrist to wrestle his hand away from the radio, the Impala swerving slightly on the road as a result.
"Hey!" Sam finally barked at him, loud enough to make Dean pause, "You're breaking your own rule here man! What are you constantly telling me? 'The driver picks the music, shotgun shuts his cakehole!'"
"But it's not even music Sam!" Dean shot back, "It's some dude talking."
"Fine!" Sam huffed, switching back to FM and turning the dial again, sliding it along until he settled on, to Dean's horror, a country music station.
"There, now it's music, and now you can shut your cakehole and go the hell to sleep."
"You cannot be serious! Country music?"
"Dean," Sam snapped in a warning, taking his eyes off the road to glare at him, and Dean glowered.
"You're such a bitch," Dean finally grumbled, crossing his arms over his chest and slinking back against the seat with a huff.
Sam elected to ignore him in favor of turning back to the road and returning both hands to the wheel.
It took less than two minutes of listening to some chick wail on about her cheating boyfriend before Dean was convinced he could feel a headache forming behind his eyes and was absolutely certain he would never be able to sleep with that crap on, no matter how low Sam kept it. This would not do.
Without a moment of hesitation, Dean slid over on the seat, going straight for the fastenings on Sam's jeans, and his brother gave a startled yelp, hand jerking on the steering wheel and making her swerve as Sam tried to one-handedly push Dean's hands away.
"Dean! What the hell are you doing?"
"Eyes on the road, Sammy," he smirked, grabbing the hand that was still trying to push him away and pinning it under his knee, and finally getting Sam's pants open.
Without preamble, he slid his hand into Sam's boxers, pulling out his cock and leaning down to suck as much as could into his mouth.
Sam gave an extremely satisfying yelp that ended with a strangled kind of sound as Dean laved his tongue silkily from side to side, still keeping up the steady, rhythmic sucking as Sam's cock started to harden in his mouth.
"Jesus, Jesus," Sam panted, eyes flicking rapidly between the road and Dean, the knuckles of one hand going white on the steering wheel and the other twisting under Dean's knee, trying to get free- in order to push him away or pull him closer, Dean wasn't sure yet.
Dean smirked around the flesh in his mouth, sliding back along Sam's length until only the head remained between his lips, then flicked his tongue around the sensitive crown and moved his hand to grip the wet shaft firmly, giving slow, tight strokes.
"Dean," Sam grit out between clenched teeth, "Let me- Christ!" he interrupted himself to stutter, hips jerking up as Dean tensed his tongue to flick the point firmly against Sam's slit, and grinning at the reaction it got him, "Just let me, dammit."
It probably said something about their relationship that Sam didn't need to clarify beyond that, and Dean released the pressure of his knee on Sam's wrist. Sam immediately yanked it free, grabbing a fistful of Dean's shirt in his fingers and pressing the heel of his clenched palm against the back of Dean's neck as he picked up the pace, head bobbing up and down in tandem with his hand.
"God, this is such a bad idea," Sam ground out, but didn't relent the pressure on the back of his neck, so Dean took this as a sign that despite what his mouth was saying, Sam was completely on board.
"Yeah, sounds like us," he pulled off long enough to murmur, before deep-throating as much of Sam's dick as he could, causing his hips to jerk and rough curses and moans to tumble from Sam's throat.
And now for the grand finale, Dean thought humorously, relishing the taste of Sam's precome sliding thick and tangy over his taste buds.
He pulled back to swirl his tongue around Sam's head again before sliding back down, spit-dampened hand curling around his brother's hip to hold him in place. He took small, shallow breaths against Sam's pubic bone as he held still, swallowing convulsively, the saliva sliding around past his lips to dampen the elastic of Sam's boxers, and it was too much, as he knew it would be, and Sam came, small "Ah!"s whimpering out of his open mouth.
Dean swallowed quickly, pulling back, his lips framing the tip of Sam's cock as he dragged the flat of his tongue against it again and again, coaxing the last of Sam's orgasm from him before sitting up, wiping his mouth with a crooked, obscene grin and tucking Sam back into his clothes.
Sam looked a little dazed, still panting as he slowly uncurled his grip on the back of Dean's shirt and returned it to the wheel, eyes sliding over to glance at him once as Dean settled back on his side of the front seat, curling his arm up to pillow his head against the door as he looked back at Sam mellowly.
Sam reached into the glove compartment and picked a random cassette, sliding it out of its case and popping in into the tape deck with a dry swallow.
Dean smirked as he settled back against the seat, perfectly relaxed by the Led Zeppelin filling the car speakers and falling easily into sleep.