
Eucalyptus cordial is a sweetened, acidified eucalyptus preparation — cooling, medicinal and very persistent. The volatile part is the essential oil, and it is the first thing to go.
Mint syrup stands in and cools in a similar way, without the medicinal note. Eucalyptus is stronger than it looks, so whatever you use, start short and taste.
Eucalyptus oil or extract
Not a substitute at any volume. Neat eucalyptus oil is toxic if taken internally; only food-grade cordials and infusions belong in a drink.
Mint syrup
What most bars actually keep. It cools in a similar way but smells sweeter and without the medicinal note, so a drink built on eucalyptus comes out softer and less bracing.
The aroma leaves before the syrup does: eucalyptus is volatile, and a month in the fridge reduces it to a suggestion. A sealed bottle holds its scent far longer than an opened one.