For one thing baking soda is alkaline. I use baking soda to remove the highly acidic nature of ACV. If you drink 2 tablespoons + water of ACV without adding baking soda, you run the risk of tooth enamel breakdown.
By adding baking soda to your ACV (before water), you will notice a strong chemical reaction and a ton of bubbles forming. This is balancing the acidity of ACV for safe consumption without the risk of tooth decay.
If you happen to have litmus test strips on hand, you can test the alkaline levels of your ACV + baking soda mixture. My tests have indicated the recipe I use results in a pH level of a little over 7.0 which is perfect.