This is a super easy method to make cold brew coffee on the road (particularly in Central American countries) when supplies and availability of normal brewing equipment is limited. I developed this method while on a trip to Costa Rica so I could have an early morning cup of coffee in prep for sunrise surf sessions.
I'm calling this "commando style" because you are making do with what you have, and it is SIMPLE and low effort to make. While it is not precise in its proportions per standard cold brewing processes, this makes great tasting, smooth coffee that will last you for at least a week (depending on how much you share with your friends).
What you need:
Qty(2) - 2 liter bottles of water with a "sports" cap
Qty(1) - Around a 250g package of ground coffee (preferable local or in-country coffee)
Qty(1) - Pointy blade (to cut and poke holes)
Duration from start to drinking coffee: ~ 2 days
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Step 1: Gather Your Supplies
You'll need to start with two 2L water bottles with at least one of them having a sports cap. The sports cap tip need to be able to fit into the neck of the bottle. One bottle needs to be full of water and one needs to be empty. Grab your bag of coffee, too. Prepping the supplies might be a little messy, so do it outside or over a sink.
Step 2: Put Coffee Grounds Into the Empty Bottle
This step can be trickier than you think if you want to keep the mess down and the coffee grounds in.
If you can't find (or make) a funnel (out of paper), one method to get the coffee in the bottle is to cut the coffee bag in the manner shown to give you a little spout to insert into the opening of the bottle. To do that...
- Fully extend the top flap of the coffee bag
- Cut a 3/4" slit at a 45deg angle to the top of the bag (see pic for which direction the 45 should go)
- Cut straight down from the top edge 1/2' in from the side down to the end of the first cut
- Remove the resulting tab. This now gives you a little spout to help direct the coffee grounds when pouring
- Put the spout into the opening of the empty bottle and slowly pour the grounds in
Step 3: Pour the Water Into the Bottle
This one of the steps where the sports cap comes in handy. Place the cap on the full bottle and then stick the tip into the bottle with the grounds. Turn upside down to start fill the bottle. As the water pours into the receiving bottle, the air should be getting pulled into the emptying bottle. DO NOT POKE A HOLE IN THE BOTTLES AT THIS POINT
Step 4: Let the Coffee Sit Over Night
Once the receiving bottle is full of water, cap it and let it sit over night for at least 12hrs but ideally 18-24hrs. Not all of the water from the first bottle will fit since the coffee grounds are taking up some space, so drink it!
3-4 times while the coffee is sitting, turn the bottle end-over-end to mix up the grounds in the water.
Step 5: Cut a Notch in the Sports Cap to Allow for Air to Escape
This can be more of a scoring of the cap, but it is important to have a means for the air to escape when the two bottles are mated together again. Once you score the cap, perform a quick test to see if air can pass by between the bottles. To do this, put the empty bottle on top if the full one with the sports cap on and gently squeeze the empty bottle. If you can hear the air come thru the notch you scored then you are good to go.
Step 6: Start the Drip Process
Now that the coffee has been "brewing" for a day, it's time to filer out the grounds and get to the good stuff. Make sure the sports cap is on the bottle full of brewed coffee. Pull open the cap and place the tip into the empty bottle. With the two bottle "engaged", carefully turn them both over, so now the empty bottle is on bottom. Set them in a corner and lean something against the top bottle to keep them in place. Using a sharp object, carefully poke a hole in (what is now) the top of the bottle with the grounds. This will allow air to come in to replace the coffee as it starts to drain out through the sports cap into the empty receiving bottle. A few grounds might pass into the empty bottle, but the grounds should eventually clog in the sports cap and only allow liquid coffee to pass through. THE CLOGGING IS A GOOD THING.
But this is where the second day comes in, as you will need to wait overnight for all of the coffee to drip into the receiving bottle. Patience. It is worth the wait.
Step 7: Cap, Chill and Enjoy!
Once all of the coffee have dripped into the receiving bottle, cap it and throw it in the fridge (or not). This is a concentrated coffee extract now that can be added to some hot water (equal portions water and coffee for strong cup) for a morning cup. Or take a swig straight from the bottle for a cool, tasty espresso strength jolt.