Steve got used to a lot of things, but he also kept some kind of basic routine. Part of that is the 'parody of domesticity' - meaning as much of the mundane shit as he could manage.

Like coffee in the morning.

"My Spanish is decent," he says, rifling through the cabinets like he lives there to start coffee and find mugs. He figures it's fair game since this place isn't even really Clint's, just a place Clint's moved into for long enough to get a job done. "I'd probably suggest you not go with a heavy breakfast and wait for lunch, but it's your stomach. You want me to go out, I'll go out."

Meanwhile, though, once coffee is working, Steve goes back to his backpack, pulls out a protein bar and tosses it, underhand, across to Clint and comes back with an energy gel pack and second bar for himself. He tears the gel thing open with his teeth, immediately.

...He also got used to riding the edge of not being able to get enough calories to support his stupid metabolism, and finding some relatively low bulk, easy transport and consume, methods of compensating. Sam gets the credit for introducing them, though.