I like to flush with grape soda. Gives it a nice flavor, much better than tasting chemicals. There's a couple other benefits of using it. It makes the plants turn a pretty purple color I mean even the ashes are purple. The buds get heavier and stickier from the extra sugar in them. Your yield will at least double or triple that of healthy plants.The co2 is also very useful for the roots. The bubbles in the soda open the pores of the roots allowing more grape flavor to be absorbed to the buds sites.
You really cant over do it so don't be shy about adding it. If you add more than you wanted you can just wring out the buds like a dish rag until you get to the level of purple you're looking for. I use fanta, not sure if other brands would have the same affect. I call it FFFFFI, Fanta flushing for flaming fucking idiots.
Next run is gonna be just straight coca cola with in dwc. It has plenty of frucose. If the plants don't have to waste energy making food it they can use all that energy making buds. I figure that will add another 25% to the yield.