Making our own cold coffee is great for enjoying coffee sans the caffeine jitters because we can control the strength and serving size.
We're no coffee experts, but here's what's been working for us.
You can buy proper equipment for making cold brew and cold drip coffee, but I'm feeling very lo-fi in the consumerism department lately, so our setup is cobbled together from un-fancy stuff.
Cold brew coffee
Cold brew is just coffee grounds steeped in cold water. We're using a metal tea strainer suspended over a glass coffee pot we found in a thrift shop. (Or you can use James Gallagher's "chilly bottle" method.)
Add 1 teaspoon of medium-sized grounds for every serve plus 1 or 2 extra for good measure. Fill the pot with cold water and leave in the fridge for 12-ish hours.
Cold drip coffee
Cold drip is made with a stack of three chambers. The top chamber holds ice that melts into the middle chamber, which is where your coffee grounds sit. The water drips through the coffee grounds and collect in the bottom chamber. (We usually "bloom" the coffee first.)
We don't have space or budget for a proper (exxy) cold drip setup, so we use two Vietnamese coffee filter cups (about $15 a pop) stacked on top of each other, both resting on a coffee pot. Come back every few hours to top up the ice — it's roughly three cups' worth of ice per single serve of coffee.
After reading that Economist article about Turkish coffee, we started adding spices to our cold brew. Mostly caraway (apparently a Croatian style but I'm struggling to find a source for this) and cardamom (Arab style, apparently from the Gulf region) but we've also tried cinnamon, clove and cayenne.
I'd recommend spicing your coffee with seeds. Pound them in a pestle and mortar to expose the oils, then combine them with the grounds before adding water.
If you're using pre-ground spice, remember that spice powder is much finer than coffee and can exit through the strainer holes. So either use a little bit or try using a paper cone as your filter (we've not tried this, but it might work since it should hold the powder in).
Add tonic water to your coffee to make it extra refreshing and summery. When using cold brew or a long black (Americano), we go a one-third coffee, two-thirds tonic water ratio. Garnish with a slice of lemon or orange.
If using espresso, you'll probably just want to top it up with tonic water (like a coffee cordial).
Corey Ginnivan's coffee lemonade was our basis for this. In lieu of cordial and tonic water, we use lemon juice (1–2 squirts from a bottle or from 1–2 wedges of fresh lemon) and soda water.