Season the chicken with salt and pepper. In a large sauce pan over medium-high heat, warm the oil. Working in batches, brown the chicken on all sides, 5 to 8 minutes total, adding more oil to the pan as needed.
Transfer to a plate. Set aside.
Reduce the heat to medium, add the onions and garlic and cook, stirring occasionally, until tender, about 2 minutes.
Add the Coca-Cola, tomato paste, sugar and stock and bring to a boil, stirring to scrape up the browned bits from the pan bottom.
Return the chicken to the pan and spoon some of the sauce over the chicken. Cover the pan, reduce the heat to medium-low and cook until the juices run clear when the chicken is pierced with a knife, about 45 minutes.Sprinkle fresh parsley and serve warm with rice on the side.