In a large bowl, whisk together the Greek yogurt, garlic, olive oil, lemon juice, ketchup, red pepper flakes, salt, cumin, black pepper, paprika, and cinnamon until smooth.

Add the chicken cubes and toss until each piece is fully coated in the marinade. Cover and refrigerate for at least 2 hours (or overnight for deeper flavor).

Preheat your grill to medium-high and lightly oil the grates to prevent sticking.

Thread the marinated chicken pieces onto skewers, leaving a bit of space between each cube for even cooking.

Grill the kebabs for 10–12 minutes, turning every 3–4 minutes, until the chicken is cooked through and slightly charred at the edges.

Remove from the grill and let rest for 5 minutes before serving to lock in the juices.