Quoted:
Note: I have tried to back sweeten apfelwein with several different unnatural sweeteners. I do not like any of them. They all have that fake sweetener taste to them.
To me the only thing to do is add real sugar. You could make up a bottle of simple syrup and sweeten it in the glass. Some even use some sort of sweet soda of the lemon lime variety to sweeten apple ciders.
One of my most delicious creations is regular apfelwein (made with apple juice) topped off with cider.
Around 3-4 oz of cider of a 12 oz bottle of apfelwein seems to be right. It's
so delicious.
Edit to say: However, in the future, I am going to try priming with corn sugar, sweetening with honey, waiting a few days for carbonation, and then pasteurizing to keep the sweetness without making bottle bombs.