01 - Place watermelon cubes and strawberries in a blender container.
02 - Pour in lime juice and sweetener if using. Sweetener amount can be adjusted to taste preference.
03 - Blend on high speed until completely smooth, approximately 30–45 seconds. Taste mixture and add additional sweetener if desired.
04 - Pour mixture evenly into popsicle molds, leaving about 1/4 inch space at top for expansion during freezing.
05 - Place popsicle sticks into center of each mold. If sticks don't stay upright, freeze for 30 minutes before inserting.
06 - Freeze for minimum 4 hours or until completely firm. Overnight freezing yields best results.
07 - Run mold under warm water for 15–20 seconds. Gently pull sticks to remove popsicles. Serve immediately.