PepsiCo (NYSE:PEP) and Yum! Brands' (NYSE:YUM) Taco Bell have come up with an innovative approach to boost fountain soft drink sales. That's having an exclusive beverage on sale -- available only at Taco Bell. According to USA Today, the new brainchild is Baja Blast, a blue soda with a lime flavor. (Despite the exotic sound, in reality it's just a new variation of Mountain Dew.)

According to the article, fountain drink sales represent 23% of sales volumes for soft drink makers, but those sales are starting to flag. Of course, that won't do, since fountain soda sales are easy money for restaurants. Dayana Yochim pointed out soft drink markups when she took a look at restaurants in Real Meal Steals.

Of course, lots of people are on to it. For to-go or drive-through meals, who needs the large drink when cheaper beverages are found elsewhere? (Of course, even a quick stop for a 12-pack of soft drinks is more cost-efficient than a large fountain drink purchased at a fast-food joint.)

While I'm not sure blue Mountain Dew will drive customers to Taco Bell in hordes, despite its exclusivity, it may indeed tempt the curious to add a drink on to their tab, at least once. Whether that temptation will hook actual loyal fans may be another matter. (If you happen to try the beverage and want to share your findings, it's likely those on the Pepsi discussion board would be glad to hear your opinion.)

What's most interesting, though, is the unusual nature of this arrangement. Over recent months, it's been interesting to note the R&D and marketing efforts of soft drink providers like Pepsi and rival Coca-Cola (NYSE:KO), both of which have ubiquitous brands and loyal customer bases but some question of where future growth in guzzling will come from.

On a somewhat similar note, Steven Mallas recently told us about Pepsi's limited-time beverages for upcoming festivities, Mountain Dew Pitch Black and Pepsi Holiday Spice.

For now, the deal between Taco Bell and Pepsi is an interesting attempt to put the flavor back into the fountain. However, whether supposedly jaded and bored soft drink consumers will begin to get lost in the parade of new soft drink flavors, colors, names, and so forth -- and ultimately become disinterested -- remains to be seen.

Are things getting soft for soft drinks? What are your favorite new soft drink flavors? Talk over the issues on the Coke and Pepsi discussion boards.

Alyce Lomax does not own shares of any of the companies mentioned. She went through a teenage phase during which if there was a soft drink that was an odd color, she'd drink it. So flash back almost 20 years, and she'd likely be all over Mountain Dew Pitch Black or Baja Blast.