Bring the fruit juice or water to a gentle simmer in a saucepan, just until warm.
In a large mixing bowl, sprinkle the unflavored gelatin powder over the hot liquid, then whisk continuously until fully dissolved and the mixture becomes smooth and glossy.
Add a few drops of your chosen bright food coloring into the gelatin mixture, stirring well to evenly tint the liquid.
Gently fold in gummy worms or candies into the gelatin mixture, distributing them evenly without breaking them apart.
Spray your brain-shaped mold with a light coat of non-stick spray or lightly oil it to prevent sticking.
Pour the gelatin mixture slowly into the mold, filling all the nooks and curves to mimic a detailed brain shape.
Tap the mold gently on the counter to release any air bubbles and help the gelatin settle evenly.
Place the mold in the refrigerator, uncovered, and let it chill for at least 4 hours or until fully set and wobbling firm.
Once set, carefully invert the mold onto a serving plate and gently tap or wiggle to release the gelatin brain.
Adjust details with additional food coloring or edible decor if needed to enhance the creepy, brain-like appearance.
Slice into chunks or leave whole for display, then serve and enjoy the gross-yet-fun Halloween centerpiece!
