Measure out the tequila, lime juice, and simple syrup, then add them into the blender.
Add the ice cubes to the blender with the liquid ingredients.
Secure the lid and blend everything on high until the mixture is completely smooth and icy, about 30-45 seconds. You should see a thick, frosty texture with no ice chunks remaining.
Pause the blender and check the consistency; if it’s too thick, add a splash of lime juice or tequila and blend briefly to loosen.
Once the mixture is smooth and scoopable, pour the slushie into chilled glasses.
Garnish with lime wedges or slices if desired, and serve immediately for the perfect icy chill.