In large nonstick skillet, melt 1 tbsp. butter over medium-high. Pour in two 1/3-cup mounds of batter; top each with 1 pineapple ring and 1/2 tsp. sugar. When batter bubbles, flip and cook until golden, 2 to 3 minutes total. Repeat with remaining batter. In bowl, mix jam with 2 tbsp. water; pour over pancakes.