I bought a $10 “nut-milk” bag and a plastic pitcher. Every night before bed, I ground up about 15 Aeropress scoops’ (570 ml) worth of espresso roast coffee — the $20 Krups grinder is fine for this, though I wouldn’t use it with an actual espresso machine — leaving the beans coarse. I filled the bag with the grind, put it in the bottom of the empty pitcher like a huge tea-bag, and topped up the pitcher with tap water (distilled water would have been better — fewer dissolved solids means that it’ll absorb more of the coffee solids, but that’s not a huge difference). I wedged the top of the bag between the lid and the pitcher and stuck it in the fridge overnight.

In the morning, I took the bag out of the pitcher and gave it a good squeeze to get the liquor out of the mush inside. Add water to the pitcher to fill to the brim and voila, amazing cold-brew. You can dilute it 1:1 or even further.

Cleanup was easy: invert the bag over a trashcan or garbage disposal, rinse off the bag, and you’re ready to go.

This produced very, very good coffee concentrate, with only a little grit settled into the bottom 3mm of the pitcher (easy to avoid). It may just be the cheapest and easiest cold-brewing method I’ve yet tried.