I am one of those people that loves the straight tonic water as my designated driver drink (when I drew the short straw). I have drank a lot of naked tonic water over the years, Canada Dry, Schweppe's, Faygo, supermarket brands, or whatever dreck out of the bar gun....etc. They started changing the flavor and getting so sweet it was hard to call it tonic and not just HFCS club soda.
Within the last few years I have discovered Fever Tree (Mediterranean is my choice); I find that the quinine to sweetness (much less) ratio is the best in this brand. It was the devil to find for a while, but recently has become easier to find (thank you Amazon) at a not so premium price. I believe its still a UK based operation, with many additional flavors of tonic on board. Since G&T was the drink of the Realm, I like the T of the UK the best.
added note, I have yet to suffer leg cramps, so maybe its working..................