Pure Riboflavin (vitamin B2) to give your drink that awesome luminous yellow/green look
Riboflavin is (apart from being the good vitamin B2) the ingredient to make your drinks glow strongly yellow/green under a UV light.
Adjust the dosage to your need BUT remenber that very, very little is needed for a string yellow colour and luminescence.
Start experimenting with dosages of 0.2g per liter liquid and then either increase it for more effect or reduce it for a more subtle shade.
At this dosage, this pack would enhance about 25 Liter of spirits for that extra conversation at your next party!