Anybody making home wine, home alcohol, will tell you "rule 1410".
For 1 kg of sugar, there is needed 4 L of water, and 10g of yeast.
That's 20% by mass. It should not exceed 22%-23% IIRC.
Even saccharimeters that I am using have end of scale at 24°Blg.
If you have extra good turbo yeast, you could try 25%,
or add sugar later, after couple days of fermentation.
This year I am making experiments with turbo yeast (there was promotion in the shop and I bought enough for couple months),
and the fastest one could make 14%-18% of ethanol from 6-8 kg of sugar (plus water enough to 25L of solution), in 48h-72h.
you should prepare couple containers, each one with different sugar proportion, write them down, say 5% more in each than previous,
and add Lactobacillus Acidophilus (or yeast or whatever you're testing).
You will see how they react for various concentrations, and will be able to compare. Or even record it by timelapse camera.
Edited by Sensei, 14 October 2016 - 10:40 PM.