The Idea Factory - The Twelve
There's an FTL capable spaceship that was massively damaged and is now adrift in deep space. Someone arrives on the ship at the start of the book and starts exploring the place, finding eleven other people on the ship already. None of them are described in any detail, and when they introduce themselves to each other, their names are One through Twelve. They're trying to fix the ship together and somehow know that it's going to explode at the end of the day.
The twist is that all twelve are the same person. When the ship explodes, they're thrown back in time the day and are stuck in a loop, each time with more people on the ship helping out. Food, water, and air might be considerations, knowing that each time they repeat the day they have to split them more, meaning they are running up against a clock. When they run out of oxygen before the ship explodes, they might not get another shot.