Xylitol works best. It is expensive but non-fermentable and tastes almost exactly like real sugar. Unfortunately it is also poisonous to dogs, cats, etc., so keep it far away from any pets.
Lactose or maltodextrin are unfermentable but not very sweet but can still add body and help take the edge off.
Other artificial sweeteners such as Splenda or stevia work okay but can have very chemically flavors. If you consume a lot of diet beverages, maybe you won't notice. But I would.
There are other ways to limit fermentation more naturally. I've explained it in detail elsewhere on the interwebs. Essentially... let your cider ferment for a week or so as cool as you can (50s Fahrenheit is ideal), then rack to secondary, then begin monitoring specific gravity every few days. Aim for 1.010-1.015. When gravity gets to that point, add gelatin to knock out most of the yeast, then a couple days later, rack again, and consider whether to add sorbate and sulfite to hurt the remaining yeast, then keep the cider cold for another month or so, trying to prevent it from refermenting. If it starts up again, add more gelatin, and sorbate and sulfite again if desired. Once the cider stabilizes fully, you can bottle or keg it. Then enjoy. Sweeter cider, but depending on how much sorbate you use, it might never carbonate in bottles, only if kegged.