Whisk 2 eggs, 1 cup milk, 1/2 cup sugar and 1/4 teaspoon cinnamon in a large bowl. Add 4 cups bread cubes and 1 cup blueberries; let soak 30 minutes. Butter a large sheet of nonstick foil and add the bread mixture. Fold in the sides of the foil and seal to form a packet, leaving room for steam to circulate. Grill over indirect heat, rotating the packet a few times, 35 minutes.