take a look at this sticky/link about stove top pasturizing and consider using sugar.
From what I've read
Lactose - pro -yeast can't digest it. Con can give a milk/creamy flavor and those who are lactose intollerant might have issues. Very good in your chocolate milk stout, but perhaps a cider would suffer.
Splenda - pro yeast can't digest it and it doesn't take like milk... con it tastes like splenda... Same with any other artifical sweetener. So the flavor could come through depending on how much you use.