All tonic water contains Quinine. It was literally invented as a delivery mechanism for the drug. Which is why it is named "Tonic Water" as it contains a tonic. Though the more stable version is "quinine hydrochloride", as listed in the ingredients.

All tonic water contains Quinine. It was literally invented as a delivery mechanism for the drug. Which is why it is named "Tonic Water" as it contains a tonic. The front label will be marked "Contains Quinine".