Sarah Sellman walked into a Larimer Square store, empty baking tray in hand. It was pushing 90 degrees outside, and the Colorado native said she needed water. But, it wasn’t for her.

Sellman, 23, had spent the day navigating the sidewalks of downtown Denver with about 20 volunteers Tuesday afternoon. They gave away nearly 1,000 cupcakes to strangers — the couple working a food truck, a bus driver, people biking to work, whoever.

“We’re just spreading the kindness, pass it on,” Sellman would say as she handed out an array of donated cupcakes, many marked by small flags with messages like “kindness is the motive” and “rely on strangers.”

The kindness spread.

Eventually Sellman came across a homeless couple at 17th and Arapahoe street. She gave them four cupcakes, noted the two looked dehydrated and promised to return.

“We need more stuff like this in the world these days,” Sellman’s mother, Julie Mordecai , said as she arranged cupcakes in Posh: Unexpected Urban Wares. Employee Jaeger Stander had invited the cupcake crew to set up inside the store so that they could beat the heat.

It registered as another act of kindness for Sellman.

Sellman, originally from Alamosa, organized “Snacks of Kindness” in collaboration with Tammy Abramovitz from the Picnic Foundation to get people involved with kindness initiatives, encouraging them to pay it forward.

“I think it’s awesome and should happen more often,” Kelly Thomas , 23, said who stopped her bicycle to grab an apple pie cupcake.

As the cupcake stock waned, Sellman remained determined to locate water, which led her to Crêpes n’ Crêpes on Larimer Street.

Restaurant manager Gabriel White listened to her story and handed Sellman two cups and a glass pitcher full of water. She gave him cupcakes.

“It’s cute,” White said about her mission, as he returned to cooking. “I like it.”

Sellman went back to the shaded sidewalk area, where Robert and Sherry Yates sat, and gave them the water.

“She’s got a good, positive attitude,” Robert said of Sellman.

Sellman’s spirit to give isn’t only directed toward Denver. Tuesday’s event was part of a larger kindness initiative that spiraled from one of her boyfriend’s mid-doze comments — he often talks in his sleep.

One night Greg Grano, 22, said: “Sarah, we have to go to Bear, Colorado.”

The catch: the location doesn’t exist on the map.

But that didn’t stop the two film school graduates from New York University , who loaded up their car in June 2010 to visit the towns of Bear in Washington, Idaho, Arizona, Arkansas and Delaware.

For 49 days, the two survived on the support and hospitality of strangers — sleeping in their homes and sharing their stories

“That was a little nerve-racking as a parent,” Mordecai said.

Grano and Sellman, who now live in Syracuse, NY, documented their trip in the soon to be completed film: ” American Bear: An Adventure in the Kindness of Strangers.”

To return the strangers’ favors, Grano and Sellman began organizing nationwide kindness events, like the cupcake giveaway, in January.

“We really like people, and we want to help,” Sellman said.

Tegan Hanlon: 303-954-1729, thanlon@denverpost.com