16 fluid ounces citrus-flavored energy drink (such as Red Bull®)
4 (.25 ounce) packages unflavored gelatin
2 cups cold vodka
Grease an 8-inch square baking pan lightly with cooking spray.
Bring energy drink to a boil in a heavy-bottomed saucepan over medium-high heat. Reduce to a gentle simmer; stir in gelatin until completely dissolved, 1 to 2 minutes. Remove from heat and let cool slightly, about 10 minutes.
Pour vodka into the gelatin mixture; stir gently to combine. Pour into the prepared baking pan.
Refrigerate gelatin mixture until set, about 6 hours. Run a knife under hot water to make it easier to cut gelatin mixture into 2-inch squares.