Stick pineapple rings and maraschino cherries all around the outside of the ham with toothpicks; place into a roasting pan. Pour 1 cup ginger ale over the ham. Cover ham with aluminum foil.
Bake in preheated oven for 1 hour. Pour remaining ginger ale over the ham, cover again with foil, and bake another 45 minutes. Remove foil and bake until instant-read thermometer inserted into the center reads at least 145 degrees F (63 degrees C), about 30 minutes more.