Members of the original Pepsi Generation are about to get a sweet trip down memory lane. The company announced on Thursday that three new "retro" sodas will be hitting beverage aisles beginning in March and April. ... The big difference? Packaging and sweetener. Pepsi Natural, touted as a "premium" cola, replaces the brand's standard sweetener -- high fructose corn syrup -- with natural cane and beet sugar, shaving four grams of sugar per 12-ounce serving. ... High fructose corn syrup has come under fire from opponents who claim that the substance -- chemically identical to sugar -- promotes obesity, though no scientific causality has been found.