What would happen if a freezer full of free drinks was left unattended on a busy street in the scorching heat?

As of Sunday, five days after the "friendly freezer" appeared near Caoyang Road metro station in Shanghai's Putuo district, the refrigerator had never run empty. It has been restocked so many times that some of the fresh supplies have had to be left out on the sidewalk where it stands.

The freezer, nicknamed "city superman depot", is an initiative launched by Cainiao, e-commerce company Alibaba's logistics arm, in tribute to and to serve outdoor workers, and it relies on the public to contribute supplies.

A banner on the unattended freezer explains that the bottled water and other beverages, as well as ice cubes and fruit, are available free of charge to outdoor workers like couriers, food deliverers, traffic police and sanitation workers.

Since the initiative started on July 19 in Hangzhou, capital of Zhejiang province, another 444 such freezers have appeared on streets in 18 cities, including Shanghai, Beijing, Tianjin, Chongqing, Jinan, Shandong province, and Shijiazhuang, Hebei province.

The public's response has been heartwarming.

In the first five days of the operation, a surveillance camera installed above the freezer in Hangzhou captured many touching moments, which were later shared online, receiving thousands of "likes" from netizens.

In one clip, an elderly man sees the freezer and places a fresh apple in it, then replaces it with a larger one.

In another, a little boy puts something in the freezer that was later found to be a letter. In it, he thanked the people who supplied the free drinks, because his father is a courier. "You made the summer even warmer," he wrote.

Similar freezers have also appeared in Shanghai.

Wei Zhan Network Technology Co spent 700 yuan ($103) to put a freezer near the Caoyang Road metro station in Shanghai, said Wang Chongjun, a manager of Chu Mo Shanghai, a major advertiser in the station.

Chu Mo Shanghai, operated by Wei Zhan, is a WeChat account that reports on the life and news in the city.

"Our purpose in joining in this initiative is to make an appeal to people to care about outdoor workers, especially during such extreme weather conditions," Wang said.

According to Wang, the refrigerator was provided by the Lawson convenience store next door, and the space belongs to Family Lu, also adjacent. Wei Zhan Network Technology considered follow-up investments to keep the freezer from running empty, but it hasn't been necessary.

"The public response has been huge," said Wang, "so active that their donations even block the way on the sidewalk."

Li Qi, who works in nearby H&M and put a box of bottled oolong tea in the refrigerator, said: "I knew of the initiative through WeChat, and I think it's more meaningful to do something instead of forwarding the story. I'll also ask my friends to participate."

A mother of an 8-year-old boy considered the initiative "meaningful" because it shows the younger generation how to appreciate and help others. Her son, Yin Letian, spent 20 yuan of his pocket money to buy some of his favorite beverages for the refrigerator.

Han Fuli, who fixes and replaces windows in Shanghai's high-rise buildings, said, "I feel happy to see the public cares about us."

Soaked in the extreme midday heat of Shanghai, where temperature ran up to more than 37 C on Thursday, Han took a bottle of water from the freezer and added, "Kind of moved, too."

Jin Tiantian contributed to this story.

heqi@chinadaily.com.cn