1. Heat grill to medium heat. Spray grill grate with nonstick cooking spray.
2. Squeeze fresh lemon juice over cut peaches and pineapple. Sprinkle with 1 tablespoon sugar.
3. Place peaches, cut-side down, and pineapple slices on preheated grill. Sprinkle with remaining sugar. Flip. Grill several minutes on each side until softened.