- Combine champagne, club soda, and sugar in a saucepan. Sprinkle gelatin on top.
- Let gelatin soften for about two minutes to bloom, then heat mixture over low heat. Stir until gelatin has completely dissolved, about 2 to 3minutes, and remove from heat.
- Stir in the rum and remaining champagne.
- Grease a loaf pan with nonstick cooking spray. Pour mixture into mold and chill for 2 hours, or until firm.
- Invert jello to parchment paper-lined cutting board and slice into squares and serve cold.
