1cup coffee grounds
Fill a 1 gallon jug with water and pour in 1 cup of coffee grounds. Stir. Cover with plastic wrap and let sit overnight, or at least 8 hours. The next morning, or after 8 hours, simply strain the coffee grounds (and save for your compost heap) and pour into another gallon container. If you're strainer isn't fine enough, place a paper towel into the strainer and strain once more. This will catch all the fine grounds that passed through the first time.
This will last several weeks in the refrigerator. The "ingredients" can be tweaked to your liking so if you like a strong cup of joe, add 1.5cups coffee to your 1 gallon of water or if you like a weak version, add 3/4cup coffee grounds to 1 gallon of water. Make it yours!
You can also spruce it up by adding some honey, caramel sauce, or chocolate sauce when you serve a glass of it.
Serve with a ton of ice and heavy cream (or not) and enjoy!