In skillet, swirl sugar over medium-high (do not stir) until melted and golden, about 5 minutes. Whisk in 1/3 cup water; stir to blend, about 2 minutes. Stir in fish sauce, garlic, ginger, and 3/4 tsp. pepper. Thread beef onto 12 skewers. Coat with oil; season. On grill pan, cook skewers over medium-high, turning often, about 4 minutes for medium. Transfer to platter. Drizzle with sauce; garnish.