Heat oil in a large pot or a skillet over medium heat. Add green beans and cook, stirring often until the beans are blistering and browning in areas, 5 to 7 minutes.
Add garlic if using and salt and cook, stirring constantly for 30 seconds.
Add water and immediately cover. Cook covered until the beans are bright green and crisp tender, 1 to 3 minutes, depending on your taste. Serve immediately.