Should I add sugar

Just picked up a gallon jubg of apple cider today. I poured out a bit to have some head room and then added a package of Red Star Champagne yeast. My question should I add some sugar to this or will it ferment on it's own sugar. If I should add how much would be appropriate? I believe it says not from concentrate on the jug. Cheers

Personally I like just apple juice and yeast with no added sugar. If you want to add sugar to raise the alcohol you can certainly do it. About a third of a pound would not be out of line.

Is there a diffrence between apple juice and apple cider? What is the difference in sugar content? I made up a batch of Welchs grape juice tonight and it took off right away with added sugar. I also did the apple cider too and it's just sitting there. Is there enough sugar to get this thing going or will I have to add sugar and repitch the yeast? Cheers

In most countries cider refers to the alcoholic beverage and apple juice is just called juice, but in the US I believe cider refers to apple juice and hard cider is the alcoholic fermented juice. Sugar content should be the same though I think most juice is diluted for consumption because it would taste too sweet for most people the way fresh juice is.
Did you rehydrate the yeast? Yeast pitched dry can get a bit of a shock, you shouldn't need to add sugar for it to start fermentation quickly.

Fruit juice will have enough sugar to ferment without adding anything else. Your apple cider may be doing something without you knowing about it. It doesn't always do anything you can really see, it just quietly sits there fermenting.

Thanks for all the responses. I checked this morning and the cider is doing well and also the garpe juice is really getting some action. I guess I was too impatient. Thanks for all your expertise! Cheers