Combine oil, juice and sugar in a shallow glass or ceramic dish. Add pork. Stir to coat. Cover and refrigerate for 30 minutes.
Thread pork onto skewers. Season with salt and pepper. Heat oil over medium heat. Add skewers. Cook, turning occasionally, for 6 to 8 minutes or until just cooked through.
Meanwhile, place couscous in a heatproof bowl. Add boiling water. Stand, covered, for 3 to 5 minutes or until water has absorbed. Stir with a fork to separate grains. Stir in orange segments and parsley. Season with salt and pepper. Add spinach. Toss to combine. Serve pork skewers with couscous mixture.