1 (20-ounce) can pineapple rings in juice, drained
1 cup grenadine
1 cup white rum
1/2 cup Campari
1 (46-ounce) can unsweetened pineapple juice, chilled
1/2 cup lime juice
1 (12-ounce) bottle ginger beer, chilled
Place the pineapple rings on a parchment paper-lined baking sheet and freeze until firm.
Combine the grenadine, rum, and Campari in a pitcher and stir until well-combined. Slowly pour in the pineapple juice, then lime juice, and finally ginger beer. Garnish the pitcher or individual glasses with the frozen pineapple rings. Serve the punch over ice.