Nature is fantastic. Our food, if eaten as intended, will provide what we need if we behave as nature intended.
Our food contains much more than needed of the electrolytes, but we wee it out normally. In heat we sweat it out more, so less in urine.
But, we need to behave as we should. No running marathons in heat, but walking slowly and shading ourselves.
Remember any tv program about an African tribe, or Aussie Aboriginies?
They walk slow. Rest in shade mid day.
Peanut butter and banana sandwich? Insult to my European tastebuds!
Also, remember, 2 or 3 days outside in the heat will be fine without any additional electrolyte intake. Eat when you are hungry, drink when you are thirsty and enjoy the nice weather!