Here's something I wrote for a themed writing challenge over on another site. I hope you will like it!
I'VE GOT WINGS - I CAN FLY!
"What's that?" Castiel asked, as he pointed to the can Dean was sipping from.
"It's Red Bull, Cas," Dean said, absently, as he scrolled through a website full of demon exorcism chants.
"What is Red Bull?" the angel asked, patiently, as he eyed the can dubiously.
"It's an energy drink. It's supposed to give you wings - not that you need those!" Dean smirked at the angel. "Here, do you want some - seeing as you're so curious about it?"
Castiel took the drink gratefully, whilst saying - "Thank you Dean!"
"I didn't think angels drank anything!" Sam commented.
"The angel doesn't but the vessel does, Samuel!" Castiel said. "The vessel's throat was distinctly parched!"
Sam watched as the angel sipped at the drink as carefully as he did everything else. He almost didn't catch what happened next - it was a case of a blink and you'll miss it moment for the younger Winchester. The angel blinked, sniffed, belched, then attacked Dean for no apparent reason, punching him in the head in an unprovoked attack.
"WHAT THE FU - " Dean shouted in surprise, as he ducked the next punch the angel threw at him. "It's not my fault you didn't like the damn drink, Cas!"
"I'VE GOT WINGS - I CAN FLY!" Castiel shouted, before running around the room, trenchcoat flapping behind him like a menacing cape of doom.
"What the hell's up with the angel dude, Sam?" Dean said, still holding his head where Castiel had punched him.
"I don't know! Jeez, look at his EYES!" Sam shouted in horror, as Cas stopped in front of Dean again.
"Look, Jerk, I've got wings!" Castiel said, as his wings unfolded from underneath his trenchcoat. "I CAN FLY, DAMN YOU!"
"What the hell was in that drink, dude?" Dean asked in horror, as he took in the angel's eyes.
Normally a pleasant blue, the angel's eyes were now an unattractive shade of black, which did not suit the face of the handsome vessel.
"Well technically it's taurine, caffiene, carbonated water and that really was rhetorical question wasn't it, Dean?" Sam asked, when his brother threw him a dirty look.
Dean yelled when Castiel gave him another punch in the head, before he said - "DUDE! For an angel, he sure can pack a mean punch! I thought angels were pacifists!"
"Not when they've been drinking Red Bull apparently," Sam said, drily. "Red Bull gives you wings and a bad attitude apparently. Must be the high sugar and caffiene content!"
Sam and Dean exchanged looks before they both leapt on the angel, who didn't want to go down without a fight.
"I'LL TAKE YOU ALL ON - YOU MOTHER - " Castiel shouted, before Dean covered his mouth.
"That's close to blasphemy," Dean told him, unwittingly throwing the angel's words back at him from a previous episode. "You should show me - some respect!"
"What do we do now?" Sam asked his brother, as they struggled against a kicking, biting angel, whose wings did insist on giving them a good clout every so often upside of the head.
"Give him some water - we'll try and flush the caffiene and sugar from his system!" Dean suggested. "I think he has an allergy to sugar - it's turning him all evil and hyperactive and everything!"
"Good idea! I'LL SAVE YOU!" Sam yelled, before leaping heroically from the angel's legs, and quickly drawing a glass of water from the nearby tap.
Dean struggled to get teh angel's mouth to stay open, before Sam forced Castiel to drink the water.
Dean's theory was proved correct, for within seconds the angel had calmed down, and he was even smiling beautifuly up at the beaten up Winchester.
"Hello, Dean! Why are you sitting on me? Who punched you? Hey, you've got feathers on your shirt!" Castiel commented, reaching up with slender fingers to pluck some shadowy feathers away from Dean.
The angel smiled again, as Dean slowly climbed off him, before helping him to his feet.
"What's that?" Castiel asked, pointing to the can of Red Bull that had been discarded on the table.
"NO! THAT'S NOT FOR YOU! STEP AWAY FROM THE RED BULL AND DRINK THE DAMN WATER!" Dean yelled in Castiel's ear. "I don't want a repeat performance of THAT little caper thank YOU very much, Angel dude!"
Castiel blinked innocently at Dean, before he did, indeed sip at the water Sam gave him, with no ill effects.
It was as if the last five minutes had not even happened. Dean watched Castiel until he was certain that Castiel was not about to act like an evil hyperactive child of doom any time soon.
He cleared his throat, returned to the lap top, and thought better of finishing off the rest of his can of Red Bull ....
THE END.
I've Got Wings, I can Fly!, by DDB
Thank you Samantha, It's much appreciated you liked! Hmm, I guess it's not advisable to give Cas Red Bull in future!! 
