Prepare a small baking dish or other container (about 5x5 inches to 6x6 inches square)by spraying with nonstick cooking spray. Set aside.
Whisk red jello and 1 cup of boiling water in heatproof bowl or glass measuring cup until the jello has dissolved. Whisk in ¼ cup of cold water and ¼ cup of chilled vodka.
3 ounces cherry jello, 1 cup boiling water, ¼ cup cold water, ¼ cup vodka
Pour into prepared dish. The jello should be about 1 inch deep.
Refrigerate jello until completely set up, about 2 to 3 hours.
Remove the red jello from the fridge and run a knife around the edge of the jello edge to loosen it. Turn it onto a cutting board.
Use a 1 to 1 ½ inch heart-shaped cookie cutter to cut as many hearts as you can from the slab of jello (I got 20). (Check to make sure your hearts will fit in the shot cups or glasses before cutting.) Return the jello hearts to the fridge while you make the green jello. Whisk Sonic green apple jello and 1½ cups of boiling water in heatproof bowl or glass measuring cup until the jello has dissolved. Whisk in ¾ cup of cold water and ¾ cup of chilled vodka. 3.94 ounces Sonic green apple jello, 1 ½ cups boiling water, ¾ cup cold water, ¾ cup vodka
Let cool to room temperature but do not let it set up.
Arrange 20 (2-ounce) shot glasses (or plastic cups with lids) on a baking sheet or rimmed tray. Place one jello heart in the center of each shot glass.
Carefully pour the green jello into the shot glasses aiming around the heart, not on the heart. Fill the glass or cup until level with the red heart. Repeat with remaining jello.
Carefully transfer to the refrigerator and let set up for at least 3 hours or until very firm. Serve chilled.