Heat a large skillet over medium-high heat. Sprinkle sugar evenly over cut sides of bok choy. Add oil to pan; swirl to coat. Add bok choy to pan, cut side down; cover and cook 2 minutes or until browned. Turn bok choy over; add 3 tablespoons water to pan. Cover and cook 2 minutes or until bok choy is crisp-tender. Sprinkle evenly with salt.