Pour ginger ale into the roasting pan. Rub brown sugar over the ham. Attach pineapple slices to outside of ham with toothpicks. Secure a cherry into the middle of each pineapple slice again using toothpicks.
Pour reserved pineapple juice into pan with ginger ale. Tent aluminum foil over the ham.
Bake ham in preheated oven for 4 hours.
Remove aluminum foil and continue baking another 30 minutes.