Halve 1 pound carrots lengthwise and cut into 3-inch pieces; steam until tender, about 15 minutes. Meanwhile, simmer 2 tablespoons cider vinegar, 1 tablespoon olive oil, 2 teaspoons sugar, 1 smashed garlic clove and a pinch of salt until syrupy, about 3 minutes. Add a pinch of red pepper flakes. Season the carrots with salt and drizzle with the sweet-and-sour sauce. Top with chopped parsley.