In a saucepan boil the sugar and sherry for 5-6 minutes. Carefully stir in the soy sauce, sugar and vinegar. Simmer over medium heat, stirring often, for 5-6 minutes until slightly thickened. Cool. Pour all into a gallon zip-lock bag and add chicken. Marinate 3-4 hours or overnight.
Stir together the mayonnaise, mustard, honey and hot sauce and refrigerate.
Grill chicken breast over a medium fire for 3-4 minutes per side, brushing with marinade often. After you have cooked each side 3-4 minutes, shake on the sesame seeds and cook each side an additional 3 minutes per side.