<P> Tonic water is often used as a drink mixer for cocktails, especially those made with gin or vodka (for example, a gin and tonic or vodka tonic). Tonic water with lemon or lime flavour added is known as bitter lemon or bitter lime, respectively . </P> <P> Tonic water will fluoresce under ultraviolet light, owing to the presence of quinine . In fact, the sensitivity of quinine to ultraviolet light is such that it will appear visibly fluorescent in direct sunlight . </P>

Where do the calories in tonic water come from