
Lime vodka is a flavored vodka — a neutral base with lime citrus added.
Vodka brings the strength and the lime note is usually flavoring rather than fruit, so it sours nothing — the drink still needs its fresh juice. Plain vodka with lime peel steeped in it gets closer and costs nothing.
Lime liqueur
The liqueur is weaker and heavily sweetened. At the same measure it both dilutes the drink and sugars it: pour about half as much and drop the syrup from the build.
Lime aromatics are the most fragile of the citrus vodkas, and they turn rather than simply fading — the bright top note gives way to a flat, slightly bitter one. This is a bottle to buy small and finish, not to keep as insurance.