In the U.S., the FDA limits the quinine content in tonic water to 83 ppm which is 83 mg per liter by mass.Now these are Wiki numbers, so use at your own risk. But, if the author is right, you would need to drink 25 liters of tonic water every day to get the dose needed for malaria prevention. Maybe you need less to act as a prophylactic for COVID, but even it you need only 10%, that's still almost three liters a day. Good luck with that.The daily therapeutic dose of quinine is in the range of 500–1000 mg.
For effective malaria prevention, 10 mg/kg every eight hours which is 2,100 mg daily for a 70 kg adult.
Never mind
The doctor got youtube censored
Mild dose of quinine better than none
Been giving my kids tonic water with OJ for colds for many years