Pour about 3 tablespoons of cherry soda into the bottom of each glass to start building your base. Add 1 tablespoon of grenadine to each glass and stir it in well. This combination creates the sweetest, densest layer, which is exactly why it needs to sit at the very bottom.
Once your red layer is set, fill each glass all the way to the top with ice. I like to use medium or large cubes here since they slow down the liquid as it pours and give the layers a chance to settle separately. Skipping this step is the number one reason layered drinks turn out muddled instead of crisp and distinct.
Grab your metal spoon and hold it upside down just above the ice in the glass. Slowly pour the lemon-lime soda over the back of the spoon so it trickles down gently instead of splashing in. Fill each glass until it's about half to two-thirds full, keeping your pour slow and steady the entire time.
Repeat the exact same slow-pour method using the blue sports drink, again pouring it over the back of the spoon. Continue until each glass is nearly full, leaving just a little room at the top. This layer floats highest because it has the lowest sugar content of all three liquids.
Drop a maraschino cherry into each finished glass and add a fun paper straw if you like. These drinks are best enjoyed the moment they're built, while all three colors are still crisp and separated. Serve immediately so your guests get the full "wow" effect before the layers start to mix.