1. To make the brine, place the salt and sugar into a large bowl. Pour one cup boiling water into the bowl and stir to dissolve. Add the cold water and place the chicken into the bowl. Refrigerate for at least six to eight hours.
2. Prepare the coffee rub by combining all the spices.
3. When ready to grill, remove chicken breasts from brine and rinse well under cold running water. Dry each piece very well using paper towels. Drizzle both sides of the chicken with oil and sprinkle with coffee rub, rubbing spices into the chicken to coat. Using either a gas grill or a grill pan, grill chicken on both sides until cooked through.