Can I use black rice vinegar for sushi rice? (Chinkiang Vinegar)
What is the difference to white rice vinegar when making sushi?
Should I still add sugar and salt?
No, you really can't. First of all the color of the rice would be off. Second, the chinkiang vinegar has a rather strong, slightly burnt flavour that I do not think would go well with sushi. I suppose if you were trying to go beyond the traditional sushi style you could try it. I guess it might work. But if you are striving towards the traditional sushi style you are probably better off substituting with normal white wine vinegar.
In fact, there is some precedent for this. 黒酢, romanized kurozu, is used in sushi at a a Tokyo restaurant called Kyo-zan, which claims to be the originator of the black vinegar sushi style.
It would likely be considered a novelty in Japan, but black vinegar was super-trendy about 6-8 years ago in Japan and all sorts of new uses, including sweetened, flavored versions meant to be diluted with water as a beverage, emerged.
There is even a product called sushi kurozu, which appears to be a diluted, sweetened form of black vinegar. Since rice vinegar is slightly diluted and sweetened for the purpose of making sushi, this seems like a reasonably un-shocking, although novel, possibility.
A recipe in Japanese suggests what appears to me to be a 3:1:1 ratio of black vinegar, mirin and sugar (estimated), plus some additional salt and dried kelp. Simmering all ingredients briefly then aging for a few days in the refrigerator would be best.
There is a history of certain vinegar substitutions in sushi, sometimes for visual effect. For example, ume-zu, which is not technically a fermented vinegar but is used as a somewhat salty, pinkish alternative to vinegar made from the remnants of pickled ume apricots, can be used partially for flavor and partially for its color. I've seen a number of apple vinegar sushi recipes online (in my experience, Japan-made apple vinegar tasted slightly milder than what we call apple cider vinegar in the US). I would not say it's a completely bizarre departure from tradition to experiment with different types of vinegar. For a Japanese palate, a novel vinegar choice would probably be less surprising than, say, the presence of cream cheese.