"Son of a bitch!"
The paper cup falls to the ground and liquid splatters across the pavement. Dean has his tongue between his lips and he might be flailing somewhat, but the barista had cautioned him that the coffee was hot, not that the coffee had been brewed by Satan himself in Hell's kitchen.
His tongue feels seared and he thinks it might fall off, and worse still, Sam just stares at him like he's being a baby, says something to the effect of 'why do I try to take you out in public.' Cas is staring too, but his head is tilting in that sort of quizzical bird look he's mastered so well, and maybe Dean would find it endearing if his taste buds were not currently shriveling up and dying right there on his tongue.
Dean is making a pained noise in the back of his throat, still trying to soothe his tongue between his lips when Cas steps forward and makes a move to pull him forward.
"I can help," Cas says, tone serious and expression even more so.
But Dean Winchester is not about to start running to the angel for every little scrape of his knee, like a toddler in need of a band-aid, so instead he replies, "I don't need your angel mojo for a coffee burn, Cas." The words sound a bit slurred as he continues to nurse his tongue.
Dean's not sure when Castiel learned to roll his eyes so well—probably from Sam, Dean thinks—but Cas huffs and does just that before tugging Dean in by the sleeve of his jacket to rumble out, "Not like that," and then the angel presses forward to mesh their mouths together, Cas licking between Dean's lips to curl around his tongue, which is still tender, but Cas is smoothing over the flesh and twisting around like a fucking pro.
It's an entirely obscene gesture in broad daylight in the middle of a public walkway, and somewhere in the background Sam is groaning and turning away, but Dean couldn't care less because Cas' lips are plush and cool and so fucking good, easing away the tingling left by the burning heat of the coffee and replacing it with a different sort of heat, wet and heady, which leaves Dean flushing and breaking away to suck in some oxygen.
The smirk on Cas' face when they pull apart is definitely not something the angel learned from Sam—Dean might be guilty of this one—but it is gone in an instant when Cas settles into his usual stoicism.
"Does your tongue feel better?" he rasps out, lips a bit more swollen and red than before.
"I think so." Dean presses his tongue to the roof of his mouth, contemplating. "But I'll need more coffee. And who's to say they won't try to sear my mouth off again?"
"It's a good thing I'm here, Dean."
There's that glimmer of a smirk again before Cas is turning around and walking on, and Dean thinks he might start requesting his coffee extra hot from now on.