Pepper
She spent most days in the basement. She couldn't quite explain it, but she felt closer to Tony here. Even though the robots were still and silent, and the computer screens completely blank, she could still hear Tony's voice prattling off in the background, talking nonsense and instructing Friday to run all sorts of calculations. That genius mind of his, always a dozen steps ahead of everyone else, spinning far too fast to be dragged down by anything as mundane as an ordinary human.
She'd absentmindedly fiddle with the ring on her left hand. She could still feel her heart racing faster as she recalled the memory - Tony, ever so casually, asking Happy for that ring. Happy, shocked and thrilled at the same time, casually remarking that he'd been carrying it since 2008. At the time, she'd kept her wits about her and played down the moment, knowing it would amuse Tony, but inside her heart was bursting at the seams with indescribable joy. Tony had loved her since 2008. Was he still out there? Did he still love her?
Bruce
He thought he was going mad. All day, every day, cooped up in his laboratory. Somehow, the whitewashed walls and the cold, emotionless instruments helped keep his own emotions at bay. He'd built a dam up, knowing that if he relented even a tiny bit, the dam would spill and everything would come gushing through. The current would sweep him up, and he would be done for.
He couldn't think about everything they'd lost, so he lost himself in his work. Running simulations, measuring gamma radiation, having nonsensical conversations with the other guy. Hulk, you absolute fool, where were you? Don't you know what we've lost?
Steve
Alcohol didn't work on him, so he drowned his sorrows at the gym. He couldn't even go for a run anymore, not without thinking about running in DC. "On your left". Now he had no one to say it to.
No, Steve went back to the good old punching bag. He could go hours on end without tiring, losing himself in the rhythm of it all. Bam. Bam. Bam. At first, he'd imagine Thanos' face on the bag, but even that was too painful, so he punched the bag and thought of nothing.
Rhodey
With Steve at the punching bag all day every day, Rhodey found his own space at the far end of the gym. Steve's incessantly, rhythmic punching faded into the background, and Rhodey threw everything into physio. The legs that Tony had given him were exceptional, but he still had to put in the work. Pull-ups, chin-ups, parallel bars. Complete the circuit and start again. And when his arms and shoulders ached, he relished the pain, because the physical pain kept the emotional pain at bay.
He was a soldier, after all. Training for the next fight. Wishing for a next fight. Wishing for a chance to set things right.
Natasha
She ran around the complex, exhausting herself with an endless self-inflicted to-do list, filled with the mindless chores needed to keep the place running. It kept her mind full and her body busy. It kept her from thinking too hard. She spent hours in the kitchen, trying to inject some flavour into their food, then spent even longer trying to coax everyone to eat something. Steve and Rhodey might wolf something down if she insisted, and if she left food for Bruce then she'd always come back to an empty plate. But Pepper was the real challenge, staring away into Tony's empty computer screens. It was a victory even to get her to drink some tea.
She'd given up trying to get the others to sleep. They would pass out when exhausted, then awaken with a start when the nightmares came. It was becoming the norm, and she wondered how long it would be until things began to get better. Would they ever heal?
Clint had come by, showing up totally unannounced despite the 96 messages she had left for him. "They're gone," he'd said in a choked voice. Natasha said nothing, but wrapped her arms around him, and he clung to her like a lifeline. Eventually he'd calmed down, and pushed her aside to see who else was here...and who wasn't.
He'd left again without saying goodbye. Natasha called him once a day, but otherwise tried not to think about him. She hadn't lost him in the Snap, but she'd pretty much lost him to the Snap.