Place the coffee grounds in a large food-safe container and add the cold water. Mix with a large spoon, then cover and allow to sit overnight at room temperature.
Strain the mixture into a clean container through a fine-mesh sieve that has been lined with two layers of cheesecloth or coffee filters. Discard the coffee grounds. Chill mixture until ready to use.
To make the iced coffee, fill a glass with ice and fill it two-thirds full of the chilled coffee concentrate. Sweeten as desired. (I made mine with 2 tablespoons sweetened condensed milk and an additional splash of half-and-half.)
Storage: The best way to store your iced coffee is separately in parts. Keep the coffee stored in a food-safe container in the refrigerator. Simply add ice and any additional mix-ins when you are ready to enjoy!
Shelf-Life: Stored separately you can keep the cold-brewed coffee for up to 1 week in the refrigerator. If you've mixed your coffee with ice and other flavors it will keep up to 8-12 hours in the refrigerator, less if it's at room temperature.
Nutritional values are based on one serving without diary or sweetener