Add pineapple and mango to a blender. Blend until smooth.
Strain the fruit puree through a fine mesh strainer into a large pitcher.
Add rum, lime juice, and simple syrup to the pitcher. Stir well to combine.
Fill Collins glasses with ice.
Pour the fruit mixture until glasses are 3/4 full.
Top each glass with prosecco or sparkling wine. Stir gently with a bar spoon.
Garnish with fresh pineapple wedges and mint sprigs before serving.
Notes
Make the fruit puree up to 24 hours ahead and store in the fridge.Use cold ingredients for the best results. Chill the prosecco and rum before mixing.Replace rum with vodka or gin if preferred. For a non-alcoholic version, use coconut water and sparkling water.Adjust simple syrup to taste based on the sweetness of your fruit.