For easy clean-up, place a cooking bag in the slow cooker.
In a small saucepan over medium heat, heat the brown sugar, mustard, vinegar, and 1/2 cup cola. Whisk until sugar is melted and mixture bubbles.
Reduce heat to simmer and cook until thickened (8-10 minutes).
Pour the remaining cola into the slow cooker.
Stud the ham with cloves and place in slow cooker.
Brush the ham with a 1/4 cup of the glaze. Refrigerate the remaining glaze.
Cook on low 5-6 hours.
Just before serving, reheat the remaining glaze and brush over cooked ham before slicing to serve.