I like to use a store-bought cold brew for this iced coffee drink. It's made by soaking coffee beans in water to extract the oils, caffeine and sugars. You can make cold brew at home but buying from a stores is a real-time saver. Cold brew also tends to be less acidic so it’s easier on your stomach. If you don’t have cold brew available, you can absolutely use regular coffee. You can simply save your leftover morning coffee and put it in the fridge to chill. Or you can make a batch to pour over ice. Keep in mind the hot liquid will melt the ice so you should aim for the coffee to be extra strong to start.