01 - Place lime-flavored gelatin and unflavored gelatin into a heatproof mixing bowl.
02 - Pour boiling tonic water over the gelatin powders and stir thoroughly until both are fully dissolved, approximately 2 minutes.
03 - Add heavy whipping cream, green food coloring, and vanilla extract to the dissolved gelatin. Blend until the mixture is smooth and evenly colored.
04 - Bundle plastic straws together with the bendable ends facing down and pack tightly into a tall glass or container so they stand upright.
05 - Carefully pour the gelatin mixture into the open tops of the straws, filling each one. Gently tap the container to eliminate any air pockets.
06 - Refrigerate the filled straws for a minimum of 4 hours, allowing the gelatin to set completely.
07 - Remove straws from the container; hold each straw under warm water for a few seconds, then squeeze or roll with a small rolling pin to extract the worm shape.
08 - Arrange the gelatin worms on a serving plate and refrigerate until serving time. For glowing effect, display under a blacklight.