Chill your glasses. Pop a couple of glasses in the freezer while you prep so your drink stays frosty.
Add the base to the blender. Combine frozen pineapple, coconut milk, rum, lime juice, and 2 tablespoons of pineapple juice.
Sweeten to taste. Add 1 tablespoon of your chosen sweetener. You can always add more later.
Blend until smooth. Start low, then increase speed.
If it’s too thick, splash in more pineapple juice or water, a little at a time.
Adjust. Taste and add more sweetener or lime if needed. For a thicker texture, add a handful of ice and blend again.
Serve cold. Pour into chilled glasses and garnish with pineapple and a cherry.