Whenever a player says sorry in training I immediately tell that player to stop saying sorry. When a player in a 1v1 accidentally steps on a player, it shouldn't immediately be apologized for. Its soccer, people get stepped on, people get kicked, it's part of the game! "Act like you've played soccer before."
Another instance is if they mishit a pass or a shot, they shouldn't also RUN to say "my bad," mistakes happen, I always respond with "don't be sorry just do it right next time."