It's an old thread, I know, but being Austrian (we speak a southern German dialect, very much akin to Bavarian) I can't keep my mouth shut about it. Funny enough, the way the word Apfelwein is pronounced is one of the things that demarcate the High German dialects (spoken in the south) from the Low German dialects (spoken in the north). In High German, it goes like Uh-pfl-vine. In Low German, the "pf" mutation has not been made, so he word is Appel, the "A" being pronounced as "uh", as in "duh!"
In the region that is famous for its production adn consumption of Apfelwein people speak a dialect that pronounces Wein "voï". And they also use the plural form of Appel, which is Äppel - pronounced as the English word apple.
As a side note, the Austrian province i live in takes pride in its apple wine, although we call it by a different name: Most (pronounced like the English word), which is traditionally produced by wild fermentation and therefore aptly nicknamed "Landessäure" ("national acidity").
Sorry for the rant, just thought it's always good to have primar sources.
Cheera