I thought adding milk to your coffee was because primative coffee drinkers did not know how to properly roast and brew the beans, causing an exceptionally acidic taste. The pH properties of milk (high base) helped to neutralize it.
With the high quality roasts that came free with CR membership, I find that milk detracts from the flavor, so I avoid it.
So as to stay on topic, I’ll add this: Soda is like candy. Drink it as a treat, not a beverage.