Why do your throat burn when drinking soda?

The carbonation in soda is a primary ingredient (without which it may not be called soda). This is carbon dioxide dissolved in water. This forms carbonic acid, which is a weak acid responsible for the tangy taste and also for the slight burning feeling when going down your throat. Some sodas also have other acids added such as Coca-Cola which contains absorbic acid, also adding to the flavor and burning feeling.