In a large saucepan, heat the olive oil over medium heat. Add chicken and garlic and cook 5 minutes, stirring frequently or until the chicken is no longer pink. Add the spinach during the last 1-2 minutes of cooking chicken.
Stir in water, tomatoes, red pepper flakes, and spice pack from couscous. Bring to a boil.
Stir in couscous. Cover and remove from heat. Let stand 5 minutes.
Stir with a fork to fluff couscous. Stir in feta cheese and pine nuts if using. Serve.