Glow in the dark ice is really easy to make. How did I do it? I opened up a bottle of tonic water, poured it into an ice cube tray, and stuck it in the freezer. Tonic water glows vivid bright blue under a black light. The glow is activated by other sources of ultraviolet light, such as fluorescent lights or sunlight, though the glow won't appear as bright in part because the room won't be as dark. If you want to duplicate the effect in the photo, you just need a black light somewhere in the room with the ice.
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.