Earlier quoted context omitted.
Tonic water can contain up to 83mg/L actual quinine. Three 2L bottles of tonic water could get you 500mg, a therapeutic dose of quinine. Unfortunately, I have not found any place that manufacturers note how much quinine is in their tonic water.
Yeah, I remember reading something similar years ago. But I suspect with the proliferation of "craft tonic water" there may be some "flavours" that don't contain quinine at all. And 6L of tonic water is... quite a lot.
Shudder.