Many breweries recommend that you can add ice to your sake but I do not.Why? Firstly, the water that makes up the ice is not the same water used for brewing - not even close! Thus, you will alter the taste of the sake. In this light I would use ice cubes made from filtered or distilled water. Secondly, most sake is already diluted from a high of 20% down to roughly 15%. When you dilute you change the structure of the sake, and I feel structure is one of the endearing qualities of sake. Typically if you were to add ice to a sake, you would add ice to a genshu which is an undiluted sake. That being said, while that is my preference, there is no right answer of course. However, I have a question, do you add ice to your white wines?