After visiting many breweries and tasting a dozen kinds of rice, they finally settled on using the same rice that makes a special sweet flavor liquor in Hunan province.

"To make sure our customers all over China can enjoy the same taste of the dregs vinegar flavor, our team has tried around 200 hotpot meals in two months, often eating four to five hotpots a day," Zhao says.

In Hainan, dregs vinegar is not a vinegar drink and the "dregs" refer to fermented rice. The soup base also includes chili sauce, garlic and red pepper.

According to Zhao, the soup base at Freshippo is pure soup, without any solids, and it has also launched an authentic Hainan flavor mixed sauce to partner with the hotpot.

"The best feature of the mixed sauce is that it can stimulate the freshness of beef, chicken and lamb, and is called 'a universal sauce' by Hainan locals," Zhao says.

Made with sesame, peanut oil, ginger and garlic, the sauce is particularly good when kumquats and chili are added.

Together with the hotpot, Freshippo also launched some fresh meat and fish products that can be boiled in the spicy and sour soup.

Zhao says that the best order in which to enjoy the dregs vinegar hotpot is to drink some of the soup first, when it's boiled, and then add cephalopods, such as squid, octopus, and cuttlefish, followed by shrimps and shellfish. Next, add slices of fresh fish, followed by vegetables.

"Finally, add a bowl of rice to the pot, which turns the soup into a sort of seafood congee," Zhao says, adding that beef and chicken are also often eaten in the hotpot by Hainan locals.

The grass carp slices pair so well with the dregs vinegar that they can be boiled for a dozen minutes without falling apart and stay crispy. Zhao says that about 100,000 boxes of grass carp slices will arrive on the shelves of Freshippo stores across the country from Guangdong every day.