Pour 1 tablespoon of oil into the same pan set to medium heat. Combine the cabbage, water, sugar, and the remaining soy sauce, sherry, salt, and pepper. Sauté for about 5 minutes until the cabbage is tender-crisp. Put the beef back into the pan and toss everything together until warmed through, which takes roughly 2 to 3 minutes. Take the pan off the burner.