Pour the light corn syrup onto a small, shallow plate. On a separate shallow plate, mix the crushed rock candy and half of the Pop Rocks together into an even layer.

Dip the rim of each serving glass directly into the corn syrup, letting any heavy excess drip off. Firmly roll the sticky rim into the candy mixture to create a thick, colorful crust.

Divide the fresh raspberries evenly among the candy-rimmed glasses, dropping them to the bottom.

Pour 2 tablespoons of raspberry syrup or grenadine over the berries in each glass.

Carefully fill each glass to the top with ice cubes, being mindful not to knock the candy off the rim.

Slowly pour the chilled lemon-lime soda over the ice to fill the glasses, creating a layered gradient effect.

Right before serving, sprinkle the remaining Pop Rocks directly onto the top of the drink so it crackles audibly. Serve immediately with colorful straws.