That said, the nation's appetite for cold coffee drinks is also booming. Japanese-style iced coffee is one of the easiest cold drinks to make at home because it doesn't require a lengthy extraction period. So what makes Japanese iced coffee so unique? Also known as flash brew, Japanese iced coffee is ready to drink immediately, unlike cold brew, which requires a much longer steep and can develop a bitter and oxidized taste. To make the best Japanese-style coffee, measuring the ingredients and creating the perfect ratio is vital; use too much ice and the flavors eventually become diluted as the cubes melt.