Image credit: John Tlumacki/The Boston Globe via Getty Images

ABC News' Paula Faris reports:

Panera Cares community cafes offer meals to customers in exchange for a recommended donation.

Operated by the Panera Bread Foundation, Panera Cares aims to raise awareness of hunger while offering items on their menu to individuals for a suggested donation, relying on community contributions to make up the difference and keep it in operation.

Nearly 18 million U.S. households suffer from food insecurity, and 16 million kids - about 1 in 4 - do not get enough nutritious food on a regular basis, according to the U.S. Department of Agriculture.

When left to their own devices, customers were surprisingly generous.

One woman ordered a meal valued at $8.99. She put in $10. Another man's lunch came to $16.57 and he willingly forked over $20.

"You walk into a restaurant thousands of times," Kate Antonacci, project manager of Panera Cares Community Cafes, told ABC News' Paula Faris. "Very rarely do you walk into one that says, 'Oh, by the way, we don't have prices."

Many customers end up donating what their meal is worth, while others donate more and some donate what they can.

"I've been here every day since the opening day," said Stephanie Scerra. "There's a mix of people that come in here, and whatever we can do to help out to the next person is what we'd like to do."

The model is so successful that the Boston location is the fifth such cafe in the country, with others located in St. Louis, Detroit, Chicago and Portland, Ore. In total, Panera Cares serves more than 3,500 people in need every week.