A recipe from chef Stefan Gates:
This isn’t a cheat, and it’s not an optical illusion — these are simply gin and tonic jellos made by adding gelatin to G&T and leaving them to set. So why are they glowing that fantastic ghostly color? The answer is that quinine (the bitter flavoring in tonic water) glows under UV fluorescent light. If you want to serve this to kids or teetotallers, it works just as well without the gin.