Apple cider comes from apples, a nutritious plant food that can and should be included as part of a Paleo lifestyle. The only problem with cider is it contains all the sugar of apples without any of the fiber. Cider is better than juice, which is almost pure sugar, but the sugar content is still high enough to warrant caution.
The Nutritional Content of Apple Cider
On the other hand, apple cider is extremely high in vitamin C and antioxidants, both of which can help counteract some of the effects of the sugar. Antioxidants help boost our immune system and lower inflammation, both of which are things we are always trying to accomplish as part of a Paleo lifestyle.
In the end, it always boils down to what you can tolerate. If you do well on an extremely low-carb diet, then you should probably avoid apple cider. On the other hand, if you feel better with a slightly higher carb content, apple cider can be an excellent way to get those carbs.
Non-alcoholic cider is more Paleo-friendly than hard cider, but if you want to indulge in a little alcohol, Mark Sisson has a place for hard cider on a low-carb diet.