I just use sodium bicarbonate (baking soda like Arm and Hammer, others use organic sodium bicarbonate). I tried potassium bicarbonate but it is tougher to source, one of the other posters said she used it. It caused me some gastro issues, so I stuck to sodium bicarbonate.
There is some good information about magnesium bicarbonate but that is tougher to source. There are some natural waters that contain it. Someone said you could make it by combining magnesium carbonate with carbonated water. I tried that and found sodium bicarbonate better.
Ted from Bangkok (earthclinic) has some good information
https://www.earthclinic.com/remedies/alkalizing_formulas.html
Another good article (this centers on mag bicarbonate)
http://drsircus.com/magnesium/magnesium-bicarbonate-alkaline-water-2/
Please read all the precautions.