Want a free Slurpee with that? This month, about 200 7-Eleven stores in San Diego are testing a GMR Marketing campaign where users can get free drinks using UBC bar codes. For customers without Internet access on their mobile phones, the coupon can be redeemed with a numeric code.

The test, which will run through Dec 31, asks consumers to send a text with the word “FAST” (or fast in Spanish, “RAPIDO”) to “72579.” In return, they will receive a message for a free beverage at 7-Eleven stores. Don’t be too thirsty though, because the offer is limited to one Spurpee, soda, Big Gulp fountain drink, or coffee per day.

“7-Eleven’s mobile test is the optimum use for our proprietary UPC bar code technology,” T.J. Person, senior vice president of Mobile Marketing Strategy for GMR Marketing, said in a statement.

The test targets both its English and Spanish customers, and 7-Eleven stores are promoting the test with bilingual point-of-purchase signage. In addition to the free drink coupon in response the test, customers will also be invited to opt in to future text messages from 7-Eleven with news and offers.

Giving away one free drink per day in order to increase customer loyalty and get mobile users to opt in to a mobile marketing program is one that we’ll likely be seeing a lot more of in 2010. As more and more businesses want to get in on mobile marketing, many retailers will test ways to get users to opt in to mobile marketing campaigns.