In a 5 gallon bucket with a blow off tube. I only made the batch 5 gallons not 5 1/2. I have a bunch of 5 gal food grade buckets I got for free from a bakery. I use them for all my non beer stuff. I use blow off tubes on them all. Easier, no worries and the big jugs of water with star san I put the blow off tubes in never need to be checked or filled for long term stuff like Apfelwein. Leaves my 3 - 6.5 gallan buckets free to brew beer.
I tasted my first batch of Apfelwein as I kegged it and it was very "white wine" tasting to me not sure if I will like it I am not a wine guy but I am sure all my friends and the gals that do drink wine will enjoy it. Plus if I can use the slurry to make Skeeter Pee which I am sure I will love it's a bonus.
The batch I just kegged and used for the skeeter pee was Apple, pineapple, Cran/rasp Apfelwein and to me it tasted better. Sweeter, more fruit flavor. Can't wait to see what the Skeeter Pee tastes like I made from it.