Vinegar was a sour liquid made from the oxidation of alcohol in wine. Types of vinegar included white vinegar and baldoxic vinegar. (ENT: "Carbon Creek", VOY: "Tattoo")
In 2367, Geordi La Forge compared the spaceborne species dubbed Junior feeding on the energy of the USS Enterprise-D to an infant being fed with milk. In order to dispose of the creature which was rapidly draining the ship's power, he realized that he had to "sour the milk" by putting "a little vinegar in baby's milk". (TNG: "Galaxy's Child")