This is the "vinegar" of the Kodava (Coorg) people in southwest India. It is made from slightly fermented juice of Gummi-Gutta fruit, simmered down to a very dark reddish-purple syrup - very sour, but also fruity. It is on hand in just about every Kodava kitchen, and sold commercially in the region, but not much elsewhere. Image from Coorg Shoppe (they ship internationally).
This is made by piling very ripe Gummi-Gutta fruit in a straining basket and setting it out over a pan for a few days until all the juice has seeped out of the fruit and into the pan. The amber juice is them put in a very deep (because it foams a lot) clay pot and simmered down until it reaches a syrup consistency. By this time it will have become a dark red-purple color. It is then put up in glass jars or bottles.
More on Vinegars & Souring Agents
The photo to the left shows ripe Gummi-Gutta (Garcinia gummi-gutta formerly Garcinia cambogia) fruit (shape varies). This fruit is also dried and used as a souring agent in Kerala to the southeast of Coorg.
Buying: This product is pretty much unavailable in North America. Same for the fruit, which is deep tropical and can't be grown reliabey even in southern Florida - and it's pretty picky about where it grows in the deep tropics too. Bottles can be ordered on-line from Coorg sources, and may get through U.S. Customs.
Storing: Once you have some, it will last for years in a sealed bottle. It slowly looses its fruitiness, but the sourness stays with it.
Cooking: Kachampuli is used mainly for meat (especially pork) and fish dishes. It is usually added near the end of cooking.
Substitutes: These have been suggested. The Essential Kodava Cookbook was written by two Kodava ladies who were brought up in Kodagu (Coorg). Shalini lives there and has made Kachampuli from ripe fruit.