Prepare the chicken by adding some yellow mustard and seasoning and rubbing it into the meat on both sides.
In a bowl, mix Coca-Cola, ketchup, minced garlic, Worcestershire sauce, and brown sugar together and set aside.
In a cast-iron skillet on medium heat, add olive oil and sear both sides of the chicken until brown (about 5 minutes per side). Pour the Coca-Cola mixture over the chicken, reduce heat to low, and let simmer uncovered for 30 minutes.
Optional: If you would like a thicker sauce, make a slurry with 1/3 cup water and 3-4 Tsp. of cornstarch. Move the chicken to one side of the pan, pour the slurry into the sauce and stir until the sauce thickens to the consistency you like. Place the chicken evenly in the pan and spoon the sauce over the chicken.