Wash and dry the spinach: Spin the washed spinach in a salad spinner or press thoroughly between kitchen towels to make sure the spinach is as dry as possible before cooking. Spinach with a lot of water on the leaves will steam in the wok and become soggy.
Chop the spinach into pieces: Remove any thick, tough stems. Chop or tear the spinach leaves into roughly 2-inch pieces. Baby spinach can be stir-fried as is.
Heat the wok: Set your wok or skillet over high heat until a drop of water evaporates within a second or two of contact.
Add the oil: Pour the oil down the side of the pan. Swirl to coat the bottom and lower sides of the wok evenly.
Stir-fry the garlic: Stir-fry just until fragrant, 10 to 20 seconds.
Add the spinach: Add the spinach to the pan all at once. Stir to mix in the garlic and coat the spinach with oil.
Stir-fry until just starting to wilt: Stir-fry the spinach until you see the edges of the leaves start to soften, 30 to 60 seconds.
Add the salt and sugar: Sprinkle the salt and sugar evenly over the spinach.
Stir-fry one more minute: Keep moving the spinach around the wok until the spinach has just barely collapsed and wilted, but is still bright green.
Serve immediately: Transfer the spinach to a serving plate and serve immediately.
