In large zip-locking bag, add sugar, mustard, salt and pepper. Shake to mix well. Place thighs in bag and shake well. Let sit for 2 minutes and shake again.
Step
Grill thighs directly over medium high heat for 20 to 30 minutes, turning occasionally.
Step
Remove from heat when juices run clear and a meat thermometer inserted sideways into thickest part of thigh reads 180°F.