a liquid medicine that has the general effect of making you feel better rather than treating a particular health problem that you might have

something that makes you feel stronger or happier

The magazine is lively and interesting - the pictures alone are a tonic. 这本杂志生动有趣——光这些图片就很有视觉冲击力。

carbonated (= with bubbles) water with a bitter taste that can be drunk on its own or added to alcoholic drinks

Two gin and tonics, please. 请来两份杜松子酒加奎宁汽水。