In this activity, learners use tonic water to detect ultraviolet (UV) light from the Sun and explore the concept of fluorescence. Learners will compare detectors using tap water and tonic water to observe differences in light from a flashlight and the Sun. Step-by-step instructions are included with photos along with important safety guidelines. This activity needs a sunny day. Activity guide includes a "What's going on?" explanation and connections to relevant science concepts like the difference in light sources, ultraviolet light, fluorescence, and quinine (a substance sensitive to ultraviolet light).