Quoted:
How fancy you want to get? Easy, but hot, homemade 20/20:
frozen grape juice concentrate
1 pack of bread yeast
3-4 pounds of sugar
water
pack of balloons, and/or some gauze 4x4s and a rubber band
food grade plastic tubing
1 gallon juice bottle or similar - something with a mouth small enough to stretch a ballon over.
Clean the bottle with bleach and rinse well. Mix all ingredents and add water until you have a gallon or so - leave a few inches of headroom, dont fill it all the way to the neck. Stretch a balloon over the bottle mouth, or use a stack of gauze and rubber band for the first few days until fermentation slows down - once it does, add the balloon. Crack the seal on the balloon and let it deflate occasionally. Let the wine work until it stops fermenting, and let the yeast settle to the bottom of the bottle. Siphon the wine off into empty liquor bottles, while avoiding sucking up the sediment.
Add more or less sugar depending on how strong or sweet you want it to be. The yeast will either run out of sugar (dry wine) or die due to alcohol content first (sweeter wine).
Daaaaannnger, Will Robinson.
I did this one time. The room was a little warm. The yeast went into overdrive and the stuff bubbled up into the balloon (it was a large one, IIRC). The balloon exploded and blew wine/yeast sludge all over the walls. It looked like a Salvador Dali painting. The room smelled gamy for some time.
Years ago I had some sour cherry trees. I made a good rose. It had a slight effervescence and was a good chilled summertime wine. I did this in 5 gal carboys with proper air locks.