Talk about your single-serve. Coca-Cola is inching up supermarket sales one sip at a time with Shop Refreshed, an in-store program that invites shoppers to drink a Coke while shopping. Coke’s been signing up grocers since May (Jewel Foods, Tom Thumb, and Jitney Jungle were among the first.) for coolers, P-O-P, and clip-on cup holders for shopping carts. Seems a refreshing beverage makes shoppers spend more: Basket rings rose as much as 25 percent when Coke tested the program last fall with four retail chains.