The grapes contain no alcohol (or very little, if they have begun to “rot” (ferment) they may have trace amounts of alcohol, but your stomach would fill up before you could eat enough to get even the little bit drunk). So the answer is, you can't get drunk from eating fresh grapes.
Consequently, what are the benefits of drinking 100% grape juice?
Some research studies suggest that red and purple grape juices may provide some of the same heart benefits of red wine, including:
- Reducing the risk of blood clots.
- Reducing low-density lipoprotein (LDL, or "bad") cholesterol.
- Preventing damage to blood vessels in your heart.
- Helping maintain a healthy blood pressure.
Is there alcohol in grape juice?
Yes, good old Welch's Concord Grape Juice. But I had to test the claims of Spike Your Juice, a yeast-based kit that ferments any 100% fruit juice, so long as it has 20G of sugar or more per serving, into an alcoholic brew with anywhere from 4-14% ABV. That puts the resulting potency somewhere between beer and wine.
Can you turn grape juice into wine?
You will still need, however, regular wine making materials such as wine yeast, yeast nutrient, wine tannin, etc. You can use other brands besides Welch's. The main thing to remember is that the grape juice can not have any preservatives that would interfere with a fermentation.