Here's my version of a sugar free Carolina style mustard based sauce:
1/2 cup Yellow Mustard
4 tsp not-too-hot sauce (ie Frank's, Cholula)
2 Tbsp Onion Powder
6 Tbsp Sugar substitute (Splenda, Truvia, Swerve, or other. Just make sure it measures like sugar)
1/4 cup Apple Cider Vinegar
1/4 cup Reduced Sugar Ketchup
Salt and Pepper to taste
Combine all ingredients in a small saucepan. Mix well. Simmer over low heat for about 8 minutes.