The juice will turn to vinegar, the sugar allows for this, you are correct. The pineapple juice is thick and gets very smelly as it turns slowly to vinegar, you must keep it covered tightly with a cloth that bugs can not get into. "IF" you had allot, cut the top off a 55 gallon drum and fill with juice, take a elestric strap and wrap around the top of the barrel with a tight cloth pulled/held by the strap. Strain maybe once a month or every 3 months and throw away the waste. In about 2 years you will have a very clear strong vinegar.