Green apple or sour?
In any case, I have one and it works fine when using normal ferment schedule. The super quick 10 day idea they recommend is not too good. Leave it for six weeks at 65-70 degrees. Then a week in the fridge. It takes 7 or 8 weeks for most beers to get done.
It will taste sort of like beer in this rig at two weeks....and it will be fully carbonated. But it is far from good tasting beer. You can let it ferment and age for the normal time. Beer needs to age.