In a large mason jar or sealable container, add simple syrup and mint - muddle for 30 seconds to release flavors. Add strawberries, pineapple, rum, water, and limeade concentrate. Shake vigorously for at least 2 minutes.
Using a slotted spoon, remove strawberries, pineapple, and mint and place into a separate bowl on the side. Remove mint and discard.
Open a popsicle bag and fill about halfway with fruit mixture, then add liquid mixture up to the fill line. Seal bag carefully. Repeat for all bags/liquid.
Published Aug 2017. Updated May 2020.