I have grape juice from store.
Maybe if I covered it well and let it sit for a couple of days, would that work?

You can make out of pretty much any juice as long as it has a grape juice base. I suggest getting the frozen concentrate. It is much easier than squashing grapes. Mix up the frozen concentrate like you were going to actually make grape juice, they put it in a large plastic milk jug.

Now it gets fun. Add the special wine yeast to the batch, and with a specially made top with the wine alcohol meter attatched, seal it tightly. After about 3-4 weeks, the meter should read around 8-13%. You don't want it any higher or it will taste gross. Then filter the yeast out of the jug a few times for optimal clarity and color. If it is a white wine, make sure you chill it before you serve it.

Have fun.

It's a little more complicated than that.

You need special barrels and other equipment.

Look up wine making. My uncle used to make his own wine, and beer.

Good luck

Wine is basically juice from fermented grapes, so I would think if the grape juice went bad that would be your wine. Now whether it is safe to drink who knows... regular wine probably goes through some type of pasteurization process to get rid of impurities.

Wine is made from grape juice. You need to add yeast and ferment it.

let it sit way past it's expiration/use by date.

You can make wine out of any kind of sweetened juice. What you need to do is to pour it into a slightly larger container, add some WINE making yeast to it, cover the larger jar with a cover but do not screw it on tight. You need to allow the gases of fermentation to esacpe. Set it in a warm spot, out of direct sunlight and let it ferment for about 4 to 6 weeks. When all the foam is gone off of the top and if you open it you get a nice soft wine smell from it, then it's ready for decantering into bottles which CAN be closed tightly. Make sure you clean the bottles, thoroughly and label them with the type of wine and the date made. Let the wine "age" for abot a month and it'll be ready to drink. Enjoy in moderation.

What Minnesota_cold said about having a grape juice base is incorrect. I make MY wines with just the juice of whichever fruit I'm using and add an eual amount of water with sugar added to it to thin it down (two cups of sugar to a gallon of warm water, mixed until the sugar is all dissolved).

Raji the Green Witch

No, the grape juice you've purchased has been pasteurized which will prevent it from properly fermenting. If it was that easy to create wine out of grape juice you would have toilet hooch recipes in prison.

The pasteurization is why fermenting apple cider (which can be purchased unpasteurized) is so popular among high school students.