From the photos, the chicken looks breaded. The sauce probably probably contains some sugar variant as well.
“Colonel Sauce” is more or less the same as ranch dressing. The unhealthy ingredient isn’t sugar. It’s oil and mono-sodium glutamate. It’s the same breaded chicken patty they put on their regular chicken fillet sandwich. You can get it grilled, if that’s an issue for you. KFC grilled chicken is low in fat, but it’s high in sodium and has MSG to boot.