The backpack, mounted using a shoulder harness, can carry up to three gallons, and it also doubles as display space for creative.

Cups are carried in a dispenser attached to the backpack or in a carry-along bag, which might also contain flyers to be passed out.

The main idea, though, is to use the opportunity to chat up the advertiser's product with passersby as they warm up over that free drink.

"It’s a great way to get people to stop and talk,” says Adam Hollander, creative producer at Brand Marketers in New York, which has used the backpacks in several campaigns. “You can target people on their way to work and give them a branded cup, a flier and some coffee."

Or you can catch them at an inauguration.

BET, out to promote the upcoming “BET Honors” awards special, showed up at Barack Obama's inauguration last month in Washington to pass out free coffee and talk up the show, which as it happens airs tonight, and its street teams were out too this morning, greeting commuters on their way to work in 10 markets across the country, again talking up the show.

This past weekend, the Jamaica Tourist Board sent a team of coffee dispensers to the New York Times Travel Show to hand out cups of Jamaica Blue Mountain coffee and talk up the country.

Both the BET and Tourist Board campaigns were managed by Brand Marketers but the beverage-dispensing backpacks are available online, with some under $100, so anyone can set up a campaign, either on their own or through their agency.