I have been using electrolyte drinks (SIS) for about a year and gradually my POTS has reduced. I recently moved to O.R.S which according to them follows the WHO recommendation and that has got rid of most of it if I take a few doses a day. I rate electrolyte replacement as a mechanism for improving POTS, I had really bad effects from it this time last year but slowly but surely it has improved with treatment. Wasn't as quick as the papers suggest for me but I was only doing once a day for a while with SIS and I often felt the need (and did) to combine with glucose since it is artificial sweetener based. 2-3 doses a day I think is necessary to make good progress for me.
Good to see the science matching my own experience of it anyway.