- Use a zester or fine grater to carefully peel the thin outer layer of lemon and lime zest, avoiding the bitter pith underneath. 
- Add the chilled Sprite to your blender jar, then sprinkle in the freshly grated lemon and lime zests. 
- Blend on high speed until the mixture is snow-like and the zests are evenly suspended, about 20-30 seconds. 
- Check the consistency — it should be smooth, icy, and bubbly all over. If it’s too thick, add a splash more soda and pulse briefly again. 
- Pour the bright, bubbly slushie into a tall glass, allowing some of the icy bits to cascade over the rim. 
- Serve immediately with a straw or a stir stick to enjoy the fizzy, citrusy burst of flavor.