Step 1: Lightly spray the inside of your plastic shot cups with a neutral cooking spray. This is an optional but highly recommended step for easy release. Place the prepared cups on a baking sheet or tray for easy transport.
Step 2: In a medium heat-proof bowl, empty the contents of the gelatin packet. Carefully pour 1 cup of boiling water over the gelatin powder. Whisk continuously for at least 2 minutes, or until the gelatin is completely dissolved. Ensure no granules remain.
Step 3: Once the gelatin is fully dissolved, add the 1/2 cup of cold water and 1/2 cup of cold vodka (or other spirit) to the mixture. Whisk well to combine thoroughly until all liquids are well incorporated.
Step 4: Carefully pour the jello mixture into your prepared plastic shot cups. An easy way to do this is to use a liquid measuring cup with a spout or a turkey baster. Fill each cup about two-thirds full.
Step 5: Transfer the tray of filled jello shots to the refrigerator and chill for at least 2-4 hours, or until completely set. For best results, chill overnight. Once firm, you can place lids on them for easy stacking and storage.