What to do with leftover whey from vinegar-based cheese preparation Whey is a valuable protein-rich by-product of cheese preparation. There are many advises for using whey came out of cheese preparation by culture. However, the whey produced after cheese preparation with vinegar (without culture) should be different.

Ricotta is prepared by boiling the leftover whey, but in my experience, the cheese prepared using vinegar is similar to Ricotta, and the remaining whey has no more cheese. Thus, I think this whey is different from normal whey referred over the internet.

Due to the presence of lots of vinegar, it should be more acidic and stronger sour taste.

For these reasons, I believe that common usage introduced for whey is not directly applicable to the whey remained from vinegar-based cheese process.

What are the suitable usage for this highly acidic (and probably cheese-free) whey?
The use of vinegar in the cheese production is irrelevant. Cheese made with the acid from vinegar or cheese made with the acid from a bacterial culture should be similar.

The difference is in how high the milk was heated when the cheese was made. The albumin in milk denatures and precipitates at about boiling temperatures. If the milk was boiled before the acid was added then you are correct that there will be no ricotta.

Many quick cheeses, such as fast mozzarella, call for the milk to be warm but not boiling. You can make ricotta from that whey regardless whether the milk was acidified with bacteria or any other acid.

As for spent whey- it is very high in acid and vitamin B. You can use it in bread in place of water.

I had read of Scandinavian desserts made from condensing whey. I tried that once and found it inedible.

Roses like acidic soil. That's where most of my spent whey goes.