Step 1

In the bottom of a large pitcher, muddle together the mint leaves and sugar.

Step 2

Stir in grapefruit juice, then rum. Cover and refrigerate until ready to serve.

Step 3

Fill cocktail glasses with crushed ice; add prepared grapefruit rum cocktail to each glass.

Step 4

Top with a splash of grenadine, if desired, and a splash of club soda.

Step 5

Garnish with grapefruit slices and enjoy!