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human
ELI5: How does some tonic water have 33g of sugar per bottle, and yet it tastes like bitter bubbly water?

I've always wondered this.... especially when a bottle of other soda has usually around the same amount, but is extremely sweeter.
gpt
Tonic water has quinine in it which is an anti-malarial medicine. It was used by the British Army in expeditions (or worse) in India and Africa to stave off malaria. 

Quinine comes from tree bark and it is extremely bitter. Thus, the quinine and water mixture is loaded up with sugar so it doesn't taste as horrible. This is also why we have gin & tonics, British soldiers had a lot of gin, quinine and sugar. Gin and sugar make quinine water tolerable.