Add gelatin powder into a medium bowl. Pour boiling water into the bowl; stir for 2 minutes.
Stir in cold water.
Place silicone cups on a baking sheet or cake pan. Carefully pour gelatin into cauldron cups. Decorate the rim with gummy worms bent in half. If the liquid is too hot, cool for 10 minutes in the refrigerator before adding gummy worms. Refrigerate for 4 hours or until firm.
Decorate jello cups with Halloween sprinkles and candy.