My recipe calls for dry hard cider.
It's a beer like angry orchard or crispin
Dry apple cider is apple cider (or juice) which has been fermented long enough to use up most of the sugar in the cider. It has an alcoholic content similar to beer and is not sweet. Whole Foods sells it in the same area where you will find beer.
Hard means with alcohol, & dry is the opposite of sweet, so low sugar content.