Start by browning the chicken. Heat oil in a skillet over medium heat and brown the chicken pieces in batches for added flavor. If short on time, you can skip this step and place the chicken directly into the slow cooker.
Combine the sauce ingredients. In a bowl, whisk together the vinegar and soy sauce. Place the chicken in the slow cooker and pour the sauce over it. Add the garlic, pepper, and bay leaves, distributing them evenly.
Cook the chicken. Set your slow cooker to low and cook the chicken for 5 to 6 hours, or until it is tender and fully cooked.
Add sweetness if desired. If you like a touch of sweetness in your adobo, stir in the sugar either into the vinegar mixture before cooking or sprinkle it over the chicken towards the end of cooking time.
Serve and enjoy. Serve the chicken adobo over a bed of steaming rice for a complete meal. This dish can be prepared a day ahead and the flavors will deepen overnight.