Are you saying they add acid so that it takes more sugar to make it taste sweet? When I went to school, they still used sugar in soft drinks. When I visited soft drink bottling plants with my father in the late 50s to very early 60s, you could always tell a clean plant from one with lax maintenance because if the sugary mess was allowed to "mellow" in places, instead of being cleaned daily, the whole bottling room took on a sour, fermentation-type of smell. In certain areas, that might have been a pleasant, familiar smell, but it was not one of cleanliness.