How to Make It
Combine sugar, peppercorns, and 1 cup water in a small saucepan. Bring to a boil and cook, stirring, until sugar dissolves; let cool completely. Strain mixture and discard peppercorns. Chill until very cold, about 2 hours.
Place cantaloupe in a blender and process until very smooth, about 1 minute. Pour through a fine-mesh strainer, pressing on solids to remove juice (you should have 1 cup juice). Discard solids.
Stir together chilled syrup, cantaloupe juice, and lemon juice in a large pitcher and chill until ready to serve.
Just before serving, add sparkling water to chilled juice mixture. Serve over ice, garnished with lemon slices and pink peppercorns.