Save yourself the time, carb it like you would a beer.
When you serve it put a sugar cube or two or honey or any other sweetener in the cup when you pour it.
With how long good Apfelwein takes to age(6+ months) too many people try to sweeten the entire batch and end up ruining it or creating bottle bombs.
Everyone's taste buds are different, even day to day you may want a dry cider as opposed to a sweet one. By not pre-sweetening the entire batch you can cater it to a much wider audience. What's mildly sweet to me tastes like a sugar bomb to my fiance...ask me how i know.