The amount of sweetness relates to how long it has brewed. If you
brewed it in a cooler area than you normally do, it will be sweeter - will have
more sugar in it. I have let mine brew to the point where it no longer has
any sugar and ends up as a vinegar because I'm diabetic. I always taste
tested it for sugar content before using because the length of time it takes to
mature differs with the seasons. So - if you do not want the sweet taste
check it before removing the shroom. The "fizzy" part is a
normal part of the process that you probably didn't notice before because you
let it brew longer. Remember too that fermented kombucha contains alcohol
and Linsay Lohan claims she failed an alcohol test because she drank kombucha
tea.
After several months of using kombucha my self I quit making it because I
found no benefits and found it to only increase my appetite which is not what I
wanted to do while being over weight.