Saturday is Bring Your Own Cup day!! Ever have a hankering to drink a Slurpee out of something loony? Like a bucket, or bowling trophy or maybe even a coconut shell? Then this Saturday, April 11 – from 11 a.m. to 7 p.m. local time – is your day. It's the first "Bring Your Own Cup Day" at the estimated 7,700 domestic 7-Eleven stores expected to participate. Folks can fill up any cup they bring into the store for the $1.49 average price of a 22-ounce medium Slurpee. Think of it as Slurpee's early "summer kickoff," says Laura Gordon, vice president of marketing and brand innovation at 7-Eleven. But this isn't just about fun-and-games. Summer is Slurpee's biggest selling season, and 7-Eleven executives are hoping that Slurpee fanatics also buy lots of hot-dogs and chips to wash down with their mega-sized drinks. But, alas, there are rules. No, your "cup" can't be a trash can (too big) or a cowboy boot (too unsanitary) or a baseball cap (too porous.) But most clean, water-tight vessels that are no bigger than 10 inches in diameter meet the requirements. The cups must be able to fit through a the 10-inch diameter hole posted on special, stand-up signs this Saturday by store Slurpee machines. A cup that just fits through the hole could conceivably hold about a gallon of Slurpee – about three times the Slurpee for the price, or roughly 100 extra ounces. Yes, that's a lot of Slurpee. Too much, in fact, for some nutritional sticklers. "At the same time stores and restaurants ask to be trusted and stake claims to being more healthy, they promote monster portions that defy imagination," gripes Kelly Brownell, professor of public policy at Duke University. Gordon suggests those who want less sugar – and fewer calories – get the new Slurpee Lite Sugar-Free Orange Creme. Even then, PR guru David Nevins thinks the promotion – which 7-Eleven has formerly held in Canada, Australia, the Philippines and Malaysia – is a stroke of genius. Except for one thing, that is. "Sounds like the promotion is also a battle between the environmentalists and the germophobics – fewer paper cups being used, but who knows where those other cups have been?" Ah, but Gordon insists that all will be sanitary. "We are very clear about this. Every store has been sent the requirements and received the training." Most stores will have someone near the Slurpee machines making sure the cups all pass the cleanliness requirements, she says. With this promotion, 7-Eleven figures each stores will attract about 100 extra guests on Saturday, which already is the chain's busiest day of the week. There's a social media tie-in, too, with Slurpee recently launching a Snapchat account under the user name REALLYSLURPEE. For those eager to cart in creative cups, but unsure what to bring, here are some oddball "cups" that customers have previously used at BYO Cup Days in Canada and Australia: plant pots, vases, tea kettles, plastic bags and, yes, bike helmets.