Freshly grind the coffee beans on the coarsest setting. If you don't have a grinder, ask a local coffee shop to grind their beans on the coarsest setting, or grind them at the grocery store. I don't recommend using preground coffee.
Place the grounds in a quart-sized mason jar or another large vessel like a pitcher. As long as you can cover it - even with plastic wrap - and the liquid will fit, you're set! If adding a cinnamon stick or vanilla bean paste, do so now.
Pour the water over the beans, working to saturate all of the grounds. As needed, use a spoon to gently mix in all the grounds to ensure that they are all wet.
Cover the cold brew and let rest on the countertop or in the fridge for 14-24 hours, as desired. I find the sweet spot is 18 hours.
Place a fine-mesh sieve over a bowl and spread a piece of cheesecloth or a nut milk bag on top of the sieve (see the post for additional straining options). Pour the coffee into the bowl to strain it.
To serve, fill a glass with ice and add the cold brew. As needed, dilute the concentrate with water, cream, or milk. Stir in flavored simple syrup as desired and enjoy!
