Combine all ingredients for marinade in bowl and stir well to dissolve the sugar.
Add chicken and red pepper slices. Cover and place in the refrigerator to marinate for at least 2 hours.
Make dipping sauce by adding all ingredients into a sauce pan. Stir and bring to a boil. Reduce heat slightly and keep on a gentle boil. When sauce is reduced to 1/3, remove from heat. The sauce will thicken with time. You can make this ahead of time, but add a little water when you reheat.
Preheat grill
Brush grill grates with oil or spray with cooking spray.
Place chicken and red pepper slices on grill grate and grill on medium heat, turning occasionally. Remove when chicken is fully cooked and peppers are charred.
In a serving bowl, layer brown rice, arugula, roasted red peppers, garbanzo beans, grilled chicken, and walnuts. Drizzles with warm sweet and sour sauce.