It's soft drink week with Coca-Cola (KO), PepsiCo (PEP) and Dr. Pepper Snapple (SNP) on tap to announce fourth-quarter earnings this week. They've grown at a slow, steady pace amid continuing expansion in India, China and other global markets. But they're rapidly evolving to meet new challenges. PepsiCo has become a dominant player in snack foods and now gets more than half its revenue from sales of snacks such as Fritos, Tostitos and Ruffles