My doc wants me to try a tsp of salt in gatorade or 1 mcg florinef (fludrocortisone) during a dizzy spell flare up. (i've had some neuro testing) but cause is still fuzzy. How will each work differently?

Maybe muscluar! Dizziness many things, inner/middle ear, central brain, heart and medications. I have seem many who have muscular trigger point disorders who will have dizziness. No doctors will investigate this issues because it is not stressed. Trigger points in the head, neck and shoulder will cause dizziness of unknown cause. I use acupuncture and myofascial tissue release + vits, minerals, magnesium, b compl.
See below. Both would raise total body sodium and therefore fluid volume which might prevent your "dizzy." the extra sodium in gatorade simply adds to your pool of fluid while Florinef (fludrocortisone) prevents excretion of sodium.