Here in Toronto, My hospital specifically recommended, soda water. (aka club soda) apparently the components of it - the sodium bicarb, etc... were the same as mixing the salt and baking soda, but this is a mixture you can drink so it heals the throat, whereas the baking soda mixture should be swished gargled and spit. They also recommend flattening it as some people become super sensitive to the fizz during rads. I for one still can't tolerate anything with fizz, and as of this coming monday I am 2 years post op and 21 months post rads.

best of luck.