Ever since Sebastian had started working for Jim Moriarty, coffee had become a whole lot more symbolic. Personally, he liked his coffee black. Simple, pure, easy. Coffee was coffee, so he didn't care about the taste as much as he did about the caffeine that woke him up properly.
Jim did care about the taste. Every time Sebastian had to come over to the criminal's loft, there would be a cup waiting for him. He had declined at first, when he had found out there was milk in there, but after a particularly confronting preach from the shorter man, he simply accepted whatever he was given, with a smile and a 'Thanks, boss.'
After a couple months, he did start to notice something peculiar. Whenever he was called in for a job, the coffee would be creamy and sweet, with a cinnamon roll on a plate next to it. Jim would eye him in silence until he finished both the coffee and the roll, and then give him an envelope with all the details, before shooing him out of his house again. "Off to work, Sebbie, dear. Later, tiger."
Milk and sugar meant business.
If he was called in because he had done something wrong - which could vary from taking too long on an easy kill to having left his shoes next to the bed if he stayed over - the coffee would be an espresso: small and very strong. Pretty much how Jim was when he was angry. An explosive shot of flavour. Those moments Sebastian liked least, because he had to sit and let the other have a hit at him until he had enough and told Sebastian to take a shower and get rid of the blood.
Espresso meant pain.
Sebastian's favourite was when he would come in and there would be a white cup with simple black coffee. He never asked how Jim found out about his preference in coffee, but he didn't care much. He would just grin and drink the coffee in one go, slamming the empty cup down on the table just in time, turning around to catch his boss and pull him close, pressing their lips together hungrily. Simple black coffee always ended in the bed, naked, sweaty, full of scratches and bruises but very content.
Black coffee meant satisfaction.
To Sebastian Moran, coffee would never be 'just coffee' anymore.