Blend the Frozen Strawberries and Basil: Add the frozen strawberries, water, and fresh basil leaves to a blender. Blend on high until completely smooth, with no visible fruit chunks or large pieces of basil. The mixture should become a bright red strawberry puree with a light herbal flavor.
Combine All Ingredients in the SLUSHi Vessel: Pour the strawberry and basil puree into the Ninja SLUSHi vessel. Add the fresh lime juice and sugar syrup, then stir gently to combine. Check the total liquid volume and add more cold water as needed to reach the machine's minimum fill line. Follow the fill guidelines in your Ninja SLUSHi manual before starting.
Select the SLUSH Preset: Turn on your Ninja SLUSHi and select the SLUSH preset. Let the machine run until the drink reaches your preferred slushy texture. The freezing time can take about 15–60 minutes, depending on the amount of liquid and how cold the mixture is when you start.
Pour and Garnish Your Strawberry Daiquiri Slush: Place a glass under the dispenser and slowly pull the handle to pour the slush. Release the handle when you have enough. Divide the drink between two glasses and garnish each with a fresh strawberry, lime slice, and basil leaf. Serve immediately while the slush is cold and smooth.