Your blood and other body fluids are supposed to have buffers that keep the PH in a very narrow range of acceptable values, so if you could influence your body PH with what you drink, it's time to go to the emergency room and get that severe metabolic disorder checked out immediately.

The only part of your body you could really influence the PH of is your stomach, and even then, assuming you don't have an acid disorder which could benefit from taking antacids, all you're doing is making your stomach work harder to restore its normal (very low) PH for no good reason.