01 - In a large mixing bowl, combine the minced garlic, lemon juice, olive oil, ground coriander, ground cumin, paprika, salt, allspice, and black pepper. Mix thoroughly. Add chicken thigh fillets and toss until coated. Cover and refrigerate for at least 1 hour, or preferably overnight, to infuse flavor.
02 - In a separate bowl, blend together plain yogurt, mayonnaise, Sriracha sauce, garlic powder, and onion powder. Season with salt and pepper to taste. Stir until smooth, then refrigerate until ready to assemble.
03 - Preheat grill or grill pan over medium-high heat and brush lightly with oil. Remove marinated chicken from refrigeration and allow to stand at room temperature for 15 minutes. Grill chicken for 6 to 8 minutes per side, or until fully cooked and lightly charred. The internal temperature should reach 165°F. Once grilled, transfer to a cutting board, allow to rest briefly, then slice into thin strips.
04 - Warm pita bread on the grill for several seconds per side or wrap in foil and heat in the oven. Generously spread yogurt sauce onto each pita. Top with shredded lettuce, tomato slices, red onion, and slices of grilled chicken. Add extra sauce as desired.
05 - Present immediately, either wrapped or as an open-faced sandwich. Enjoy while warm.