Tonic water in perfumery is usually an accord rather than a literal extract, built to suggest chilled bubbles, citrus peel and the dry bitterness associated with quinine. Its effect is brisk and transparent, giving an opening a clean, lightly mineral edge rather than the sweetness of a conventional soft drink.
In men's fragrances, it commonly appears near the top of the pyramid, where it sharpens citrus, gin-like juniper, herbs and airy woods. On its own, the impression is fleeting; paired with musk, vetiver or cedar, it makes a composition drier and more polished. Look here if you prefer fresh scents with an aromatic, slightly bitter twist instead of dense sweetness or heavy spice. Deeper woods give the accord more presence after the opening.