If you’re not familiar with making cupcakes, a simple vanilla cupcake is a great place to start. You can even make cupcakes from cake mix or buy pre-baked cupcakes from the bakery section if baking from scratch isn’t your thing! Avoid cupcakes with fillings, as these may not be sturdy enough to stay intact through the dipping process.

Diet tonic water will also work for making glow-in-the-dark cupcakes, if that’s what you have on hand. You can use pre-made buttercream, but the addition of the tonic water in this frosting will make your cupcakes glow brighter!

If you’re using a hand whisk, it will probably take closer to 10 minutes for the frosting to reach the right consistency.

Reserving some of the tonic water at first will help you get a stiffer consistency for your buttercream. Adding it back in will help smooth it out, so it stays stiff but is still creamy enough to pipe onto the cupcakes.

White icing glows the best. The darker you make the icing, the less it will glow. If you’re using another flavor of gelatin, pick a color that matches! For example, you could use red food coloring for strawberry gelatin, or yellow if you’re using lemon or pineapple.

If you don’t have a piping bag, you can put the buttercream into a large resealable plastic bag. Then, use scissors to snip off just a little of the bottom corner.

Start with just a little icing on each cupcake to ensure you have enough to frost each one, then go back and add more. Try to divide the frosting evenly across all 12 cupcakes. This should be about 2 tbsp (32 g). If the icing slides off the cakes, don’t fret. Simply pop the piping bag in the fridge for a few minutes to help the icing stiffen. If you have different tips for your piping bag, a star tip really emphasizes the glowing effect![8] X Research source

Start with just a little icing on each cupcake to ensure you have enough to frost each one, then go back and add more. Try to divide the frosting evenly across all 12 cupcakes. This should be about 2 tbsp (32 g). If the icing slides off the cakes, don’t fret. Simply pop the piping bag in the fridge for a few minutes to help the icing stiffen. If you have different tips for your piping bag, a star tip really emphasizes the glowing effect![8] X Research source

When the cupcakes are ready, the frosting should be hard to the touch.

Your saucepan should be big enough to hold 2 cups (470 mL) of liquid, but it shouldn’t be too big, or the gelatin mixture won’t be deep enough to completely coat the icing. A 1–1 1⁄2  qt (950–1,420 mL) saucepan is a good option for this. If you don’t have a small saucepan, boil the water in a larger saucepan, then pour it into a heat-safe bowl after you add the gelatin.

You can experiment with different flavors of gelatin, if you’d like!

The tonic water will react to the UV light, which is what causes the cupcakes to glow.

If the gelatin sets up, you’ll have to make a new batch, as it will be impossible to coat the cupcakes.

If you’re worried about the cupcakes getting warm while you’re dipping them, just take them out of the freezer 2-3 at a time. It’s fine if a little of the gelatin drips onto the bottom of the cupcake, but try not to saturate the cake or it might fall apart.

Stir the jello after each batch. If the gelatin starts to get too thick, you can dip each one 4 times. However, dipping them 6 times will produce a better glow.

If you have any leftovers, you can keep them in the fridge for several days.

The glowing effect will be more obvious at night.