Sales of Coca-Cola and Pepsi declined 15-17% in April-May compared to the previous year due to increasing demand for non-carbonated drinks. While carbonated drinks currently have the largest market share in India, there is a shift in consumer preferences towards non-carbonated drinks due to growing health awareness. However, carbonated drinks may still dominate the market due to factors like poverty and illiteracy that slow the shift towards non-carbonated drinks.