Wash and dry the grapes thoroughly with a clean dish towel to ensure the candy coating sticks well.
Insert toothpicks or skewers into the stem end of each grape, creating a handle for dipping them in candy.
In a medium saucepan, combine granulated sugar, light corn syrup, water, and your chosen flavoring.
Bring the mixture to a boil over medium heat.
Allow the mixture to cook, without stirring, until it reaches 300°F (hard-crack stage) on a candy thermometer.
This is crucial for that signature crack crunch!
Quickly dip each grape into the hot syrup, then roll it in pop rocks candy while still sticky, coating thoroughly.
Place on parchment paper to set.