In a small bowl, drain juice from 1 can of peaches - discard juice from the other can. Add sugar and cinnamon to the juice. Mix well. Place sliced peaches in a 13x9x2 inch aluminum pan. Pour juice mixture over peaches. Evenly spread box of cake mix over peaches. Cut butter into tablespoons - dot evenly over cake mix. Cover pan loosely with foil. Set on even campfire grate with even heat for about 15 minutes or until steam begins to escape. Once you see steam, remove pan from fire but do not remove foil from top. Let pan rest for ten minutes until cake mix is absorbed and begins to form a crumbly crust.