This stuff is around because growing in hydroponics causes the roots to be bathed constantly and some oils are lost, so some secondary metabolic processes of the plant don't happen, those are involved with taste and aroma development. So to boost the secondary metabolism, we increase the acid and carb content of the plant to get the primary metabolic systems working right.
One way to do that is add some cane sugar and citric acid to your res. And those are the main ingredients in Sweet. You could save your money and just buy those separately, or some guys just use Lipton Instant Ice Tea Powder, apparently it has citric acid and some kind of sugar.
HTH