Preheat your oven to 350-F and line a large rimmed baking sheet with foil, or coat it with cooking spray.
Place the ham in the pan. Mix the dark brown sugar, Dijon mustard, paprika, cornstarch, and red pepper flakes in a small bowl. Rub the sugar mixture all over the ham, pressing a bit in between the slices.
Drizzle the cola over the ham slowly so that it seeps in between the slices.
Cover the ham loosely with foil and bake for 90 minutes. Remove the pan from the oven and baste the ham with the pan juices. Return the ham to the oven, uncovered, for another 30 minutes.
Transfer the ham to a large platter and serve!
Notes
A fully cooked spiral ham needs to bake for 10 minutes per pound at 350 degrees.