i make lots and lots (and lots) of wine from store bought juice. usually 2 jugs fill my 1 gallon carboys perfectly. if you are going to ferment in the container, you'll have to pour some juice out to make room for the sugar and the bubbliness of active fermentation. save the extra juice and add it back after 3 or 4 days when the bubbling is not quite so overactive. if you are not doing a whole gallon, you'll probably have to cut these numbers in half, but here are the amounts of sugar that i use:
grape juice: 1.15 cups sugar/gallon
apple juice: 2.25 cups sugar/gallon
white grape peach: 1.1 cups sugar/gallon
cranberry juice: 1.7 cups sugar/gallon
cranberry pomegranate juice: 1.7 cups sugar/gallon
pomegranate cocktail: 2.25 cups sugar/gallon
they are fermented to dry in a couple of weeks, but you're sure to make a pirate face after the first sip. in my opinion, these are positively drinkable after 3 months, and absolutely delicious after a year. i dont backsweeten either, they're perfectly dry to my taste.