I am so glad that commercial vegan coffee drinks are available now, but it is much cheaper to make them at home. All you need is coffee and plant-based milk. You can use any variety of plant-based milk; just add a little sweetener if it's not sweet enough.
Another nice thing about making your own iced coffee drink is that you have the option of using decaf coffee.
I use cold brew coffee because it holds up so much longer (weeks!) in the fridge compared to normally brewed coffee. If you do brew a cup of coffee and then cool it down in the fridge, use it soon!
To make the cold brew coffee: A good ratio of coffee to water is 3/4 cup of ground coffee for every 4 cups of water. Put the ground coffee in a nut-milk bag (or any small mesh bag). Soak the coffee in water at room temperature for 12-24 hours. Finally, remove the bag and squeeze out any remaining liquid.
To make the drink: Pour the coffee and milk into a bottle, and shake to mix. Add sweetener if it's not sweet enough.
cost per bottle (16 oz)
ground coffee: $0.37 (assuming coffee is $10.00/lb)
soy milk: $0.37
total cost: $0.74