This is an idea that is very popular with alternative health and diet enthusiasts. They often discuss eating an alkaline diet to alter your body's ph levels. There is not a lot of formal science behind the idea, which does not mean there is anything wrong with it, just that it is hard to say with hard scientific fact that it makes a difference in your health. Some people use baking soda in water as an antacid as well. I can't really link to any scientific studies regarding this practice as a positive because I can't find them.
It is possible to overuse baking soda and have a problem with high sodium levels as noted in the abstracts I'm linking below. It seems the amount of soda you are discussing is small and wouldn't be dangerous if you have good kidney function but as always, discuss it with a health care practitioner who is familiar with your medical history just to be safe.