I have spent a fair amount of time looking into this the last few weeks so I’ll tell you want I’ve found but I’m very far from an expert. Unfortunately I didn’t keep good track of citations for everything I learned but I’ve included a few references below that may be of interest to you. It’s also not certain that supplementation to achieve a particular Na:K ratio will produce the health outcomes associated with an optimum ratio.
A Na:K ratio greater than 1 typically correlates with negative health outcomes (risk of stroke, heart attack, cardiovascular disease, etc). Potassium seems to offer a protective effect against the harms of too much Sodium particularly in terms of blood pressure. I have seen various sources recommending Na:K ratios 1:2 or 1:3. I have not seen any sources that point to any harm or risk to having even more K favoring diet like 1:4 or 1:5.
How much Na and K to take to avoid depletion during extended or cyclic fasting compared to how much to take after vigorous exercise is probably not the same. It would depend on how much of each you tend to lose in sweat. Apparently, these amounts can vary widely between individuals.
My suspicious is that most commercial electrolyte mixtures are hesitant to put as much Potassium as would be ideal because of the harsher taste of Potassium compounds and the perceived risks of excessive Potassium supplementation.
Personally, I am aiming for 2-3g Na and 6g K for a 1:2 or 1:3 ratio per day.
Jayedi A, Ghomashi F, Zargar MS, Shab-Bidar S. Dietary sodium, sodium-to-potassium ratio, and risk of stroke: A systematic review and nonlinear dose-response meta-analysis. Clin Nutr. 2019 Jun;38(3):1092-1100. doi: 10.1016/j.clnu.2018.05.017. Epub 2018 Jun 1. PMID: 29907351.
Okayama A, Okuda N, Miura K, Okamura T, Hayakawa T, Akasaka H, Ohnishi H, Saitoh S, Arai Y, Kiyohara Y, Takashima N, Yoshita K, Fujiyoshi A, Zaid M, Ohkubo T, Ueshima H; NIPPON DATA80 Research Group. Dietary sodium-to-potassium ratio as a risk factor for stroke, cardiovascular disease and all-cause mortality in Japan: the NIPPON DATA80 cohort study. BMJ Open. 2016 Jul 13;6(7):e011632. doi: 10.1136/bmjopen-2016-011632. PMID: 27412107; PMCID: PMC4947715.