01 - Combine the watermelon cubes and strawberries in a blender container.
02 - Pour in the lime juice and sweetener if using. The sweetener is optional and can be adjusted to taste preference.
03 - Blend on high speed until completely smooth, approximately 1-2 minutes. Pause to taste and adjust sweetness if needed.
04 - Pour the blended mixture evenly into popsicle molds, leaving about 1/4 inch space at the top for expansion during freezing.
05 - Insert popsicle sticks and freeze for at least 4 hours or overnight until completely firm.
06 - To release popsicles, run the mold briefly under warm water for 10-15 seconds, then gently pull out the sticks. Serve immediately.