Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, alternating with the grape soda. Mix until just combined, being careful not to overmix.
Divide the batter evenly among the prepared muffin cups, filling each about two-thirds full.
Bake for 20-22 minutes, or until a wooden skewer inserted into the center of a cupcake comes out clean.
Let the cupcakes cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely.
Make the Frosting
In a medium bowl, beat the softened butter until creamy.
Gradually add the powdered sugar, alternating with the grape soda, beating until smooth and creamy.
Stir in the vanilla extract and purple food coloring (if using).
Decorate
Once the cupcakes are completely cool, frost them with the grape soda frosting. Enjoy!
Notes
For an extra burst of grape flavor, you can add a tablespoon of grape extract to the cupcake batter. Make sure the cupcakes are fully cooled before frosting, otherwise the frosting will melt.