Quinine has a remarkable bitterness to it. Touch a bit to your tongue and you will never forget it.
Tonic water has a small amount, but it is in a fairly sweet vehicle combined with other flavors. It would take about one and a half grams to get the same amount in 5 gallons of beer but would the beer be sweet enough to offset the flavor. I've done the taste test (LOL) and personally do not think so, besides the fact that quinine has bacteriostatic qualities and prevents the growth of yeast.
As to how much quinine will kill yeast ??? It's been a 40 years since I studied pharmacognosy.
For the gin and tonic flavor look more into juniper berries and lemon/lime.
I'd try a few teas made with hops - citrus - juniper before trying the quinine.
OMO
bosco
ps. As an afterthought I think a solution of quinine and water would repel sharks and make them avoid the area for a long time, that is if they respond to disgusting tastes like we do..LOL I am surprised that it has never been tried