In a bowl mix the chicken, garlic powder, oregano, lemon juice, oil, and season with salt and pepper.
Make the sauce: Mix all of the ingredients for the sauce in a bowl until smooth. Add water, about 1 teaspoon at a time as needed to thin it out to a creamy sauce. Season with salt and pepper to taste. Set aside.
Heat a nonstick pan on medium heat. Once hot, add the oil. Brown the chicken mixture until it is no longer pink and cooked through. Season with salt and pepper to taste as needed.
Warm the taco shells on both sides in a pan over medium heat for approximately 10 seconds per side.
Mix the ginger ale and grenadine to taste for a hint of sweetness. Serve over ice if desired.
Layer the taco shells with chicken mixture, lettuce, tomato, onion, cilantro, sauce, and feta. Serve with hummus, pita chips, and ginger spritzer.