Glowing Ice Flavor Tips
Personally, I think tonic water tastes vile, so I have a couple of tips for improving the flavor of the ice cubes. The first tip is to dilute the tonic water. If you mix the tonic water with normal water your ice cubes will last longer (pure tonic water cubes melt fairly quickly) and won't taste as much like quinine (the ingredient responsible for the glow). Otherwise, you can cut it with lemonade or another sweet-sour drink that won't suffer from the bitter tang of the quinine. The second option is to put the ice into a drink where the flavor is desirable. The obvious choice would be to use the ice cubes in gin to make a gin and tonic. Non-alcoholic choices include fruit juice, Mountain Dew™, or Kool-Aid™. Don't worry about diminishing the glow from the ice. This photo is of tonic water ice and water.
Types of Tonic Water
The tonic water has to contain quinine. It doesn't make a difference whether you use diet or regular tonic water, just be sure the label lists quinine. Some brands contain more flavoring than others, but I have had equally good luck with inexpensive store brands and premium brands. Another tip is to use clear plastic cups instead of glasses. Most plastic cups are brightly fluorescent under black light, so you get an added glow if you use them. You might want to take a mini-black light with you when you go shopping, to see what else will glow for you.