Pour the grape jello mix into a medium mixing bowl.
Add the boiling water to the jello powder and stir continuously until the powder is completely dissolved, about 2 minutes.
Stir in the red berry vodka and lime juice, mixing well to combine all ingredients evenly.
Arrange your shot cups on a tray or baking sheet for easy transportation to the refrigerator.
Carefully pour the jello mixture into each cup, leaving about 1/4 inch of space at the top to prevent spilling when moving them.
Place the filled cups in the refrigerator and chill for at least 2 hours, or until the jello is completely set.
If desired, just before serving, top each shot with a small dollop of whipped topping and a sprinkle of purple sanding sugar for an extra festive touch.
Notes
Make sure the jello is completely dissolved in the boiling water before adding the cold ingredients to ensure a smooth texture.
For the best-looking shots, let the mixture cool slightly before pouring into cups to prevent bubbles from forming.
If you want stronger shots, you can increase the vodka slightly, but don't exceed 1 cup of total liquid for the alcohol and lime juice combined, or your shots won't set properly.
For cleaner edges when serving, briefly dip the outside of each shot cup in warm water to help release the jello from the sides.
If you're making these for a party, prepare a tray with additional garnishes like lime wedges or berries so guests can customize their shots.