From my previous attempts, if you try to ferment sugar water with Young's or any other wine yeast, those yeasties will turn around and tell you to get stuffed, no matter what you add in the way of nutrients.
I have only ever tried baker's yeast once, and they didn't get much further, but I've never tried feeding and coaxing them as Robbo suggests.
i have made a wash to 9% with youngs super wine yeast using normal nutrient with juice from a lemon. it fermented out in normal time then i added orange cordial and did a 2nd ferment with that. i should imagine it will work with more sugar and maybe another tsp of nutrient but my attempt turned out horrible.
tbh not much of a wash expert- i stop at 9% - simply because its quicker and easier and the champagne yeast at those lvls needs only minimal nutrients(boiled baking yeast is good), doesnt need fining, or carbon and adds a nice taste- also it drops clear v fast
if desperate to hit 18%, champagne yeast, lots of nutrients and add the last kilo in stages -or alcotec yeast and get ready to filter it