As a part time brewer in a previous life I can explain. Yeast multiplies in the presence of air, so a small amount of yeast will become a lot of yeast until you seal the bottle and exclude the air. When sealed from air it ferments the sugar and produces equal volumes of CO2 and ethanol. The sugar you use is a complex sugar so the yeast has to split it to simple sugars before fermenting it so that will slow the reaction slightly I guess. Brewers often use invert sugar which is simple sugars and ferments quicker. You can also feed the reaction by adding food for the yeast (yeast nutrient) that you can buy from a brewers supply shop. A small amount of marmite is the cheapest. Wine yeasts are stronger than beer yeasts and will ferment more sugar for longer. The yeast will ferment until it runs out of sugar or is inhibited by the amount of ethanol present. Make wine and waste not assuming you are old enough.