Fill a large mixing bowl halfway with ice cubes or crushed ice, creating a mound of icy shards.
Pour the chilled Sprite over the ice, filling the bowl about three-quarters full for a fizzy, bubbly base.
Add a squeeze of lemon juice and a teaspoon of sugar if you like a sweeter, more citrusy kick.
Let the mixture sit for about 5 minutes, watching the bubbles rise and the soda start to cool the ice further.
Using a spoon or spatula, gently stir and mash some ice against the sides of the bowl to accelerate melting and create a slushy texture.
Continue stirring for about 8-10 minutes until the mixture turns opaque, slightly thick, and resembles a snow cone or slushie.
Taste the slushie; if it's too watery, add a bit more soda and stir again. If it's too icy, let it sit for a minute or two to soften.
Transfer the slushie into a tall glass or cup, garnish with a sprig of fresh mint or a lemon wedge for a finishing touch.
Serve immediately and enjoy the fizzy, icy burst of summer flavor with a straw or spoon in hand.