Preheat the oven to 350 degrees F (175 degrees C). Rinse and pat dry the pork roast.
Cut deep slits all over the roast with a sharp knife to different depths. Press pieces of garlic into the slits. In a small bowl, mix together the water, brown sugar, and the maraschino cherries with their juice.
Place the roast in an oven bag, and pour the cherry mixture over. Seal the bag, and place in a roasting pan.
Bake for 3 hours in the preheated oven, or until the internal temperature of the roast is at least 145 degrees F (63 degrees C).
Remove from bag to a serving plate, and baste with the juices.
Let stand for 15 minutes before carving and serving.
