ancient people were not stupid... they had what became known in the Americas as farmer's punch, switchel, or the Dr. Jarvis variant, honegar. which was, for lack of lemons, ACV and honey or maple syrup and grated ginger... at times with added salt.
Gatorade was, more or less, a for profit spin off on switchel.
Southeast Asians actually seemed to have the lemon drink down long ago... but then the citrus is native to Asia... they would preserve the lemons by fermenting them and then putting them in a salt brine (you can do this with apples too... the lemons, they would mash up, rind and all, sweetened to taste and served as *lemonade*.
Something like this - Chanh Muoi
We have several Vietnamese restaurants here that serve the *real* thing, rind and all - it looks rather unpleasant with the seeds and rind in there; it isn't everyone's cup of tea... but I really like it alot - especially here on hot desert summer days.
the real stuff with the added *probiotics* would be great if anyone chose to make it...