Stevia has no calories and no nutrition in it. So, they were just drinking lemon water.
I tried Agave syrup today and it tastes just fine, no flavor that I could detect. I read about John Rose. A Health counselor who oversees many people doing the MC(as well as other cleanses) - and often his people do long MCs just fine with Agave.

I am interested in any actual nutritional comparison to Maple Syrup and cannot find that so far on the web.
My hunch says that it is a good substitute or a nice change from the Maple Syrup - but Stanley Burroughs did not have access to it back then.

Best,
LN