Castiel had taken to coffee like a baby takes to milk.
Newly human, he wasn't quite sure about maintaining a regular sleep schedule, and therefore was reliant on caffeine to keep himself awake during day-time hours.
Especially because Dean and Sam wanted to teach him how to hunt, human style.
It didn't take long for Castiel to start sleeping regularly, but he liked coffee so much, he didn't reduce his intake of it.
He drank coffee like Dean drank beer.
It didn't help that he had taken a special liking to Starbucks coffee. All the different flavours, all the specialties, every drink tasting slightly different, every time he drank it.
The Starbucks nearest to the Bunker had grown to know Cas' face, and had even taken to asking him if he wanted his 'usual'.
Sometimes Cas would go to the coffee shop, if he ever needed some alone time, or if he just wanted a drink, never coming back empty handed, though. He'd always bring back some sort of treat for each of the brothers, both not particularly caring for the fancy coffee - usually it was a pie for Dean, and another sort of pastry for Sam, or sometimes a pack of a particular brand of beer he knew both Winchesters liked.
—
One evening, when Cas had gone on a trip to his favourite coffee shop, there was only enough time to order his drink - the shop closing a few minutes after. So, for once, he brought his drink back to the Bunker.
The plastic bag with two packs of beer inside was deposited on the table, and the blue-eyed man finally took a sip of his drink. It was the best coffee he had ever purchased, and his eyes lit up with delight.
Only the elder brother was in the kitchen with him, and his interest was peaked slightly. Especially by the moan of complete satisfaction the dark-haired man also let out.
"That coffee can't be that good." The blond raised his eyebrow, glancing sceptically at the cup.
"It truly is, Dean!" Castiel exclaimed joyously, offering the drink to the taller man. "Try some!"
Knowing the fallen angel wouldn't let him off until he tried the drink, he took a sip of the coffee.
He completely understood Cas' fixation with the drink, even if they only tasted half as good as the beverage he was holding.
Somewhat unwillingly, he relinquished the cup back to Cas, giving the drink a stare of longing.
Castiel didn't notice, and finished his drink, while getting some popcorn and other snacks ready for the planned movie night.
—
The next time Cas told the brothers he was heading to Starbucks, Dean offered to go with him. Happy to having the company, Cas told the taller man to lead the way, and they took the Impala to the shop.
"Are you planning on getting a drink?" Cas asked, looking wide-eyed at the blond,.
"Yeah, get me one of whatever you're having. I'm not sure what's good."
After making some small talk with the barista, Cas finally ordered the drinks.
The shop was fairly empty - one reason Cas was particularly fond of this shop - so their drinks were made quickly.
One sip, and Dean was hooked.
—
After that day, Dean would offer to go with Castiel to the coffee shop every time he planned on going.
If he wanted to go on him own, he had to come up with a lie, though he would always bring the elder Winchester back a drink afterwards, claiming he ;stopped in on the way back'.
Sam told him, one morning, when Dean was particularly excited about a prospective case being located right next to a Starbucks, "you've created a monster, Cas!" but he was laughing, so the fallen angel didn't feel too bad.
He was slightly embarrassed, though, so he put his face in his hands, and groaned out an "I know!"