I recently had to experiment with this because half of my F2's didn't fizz at all. I left them for like 2 days, opened them, and there was absolutely no pop, it was like I opened a bottle of water. I added some more sugar to them and left them for another 2 days, and 2 of them did get a lot of fizz, but the rest did not. I am not sure what I did wrong here, but I can say that it works, even though half of the ones I added sugar to didn't fizz, the other half did! So it does in fact work!
Also, at that point, I didn't care to measure how much extra sugar I put in, I just poured a little bit in each bottle.
I count my F1 containers as 1 batch each. But I have heard of people counting their F2's as batches, since from 1 container of F1 they could make 4 different F2 flavors, each their own "batch".
