If you want to enjoy sake more, temperature is one of the key factors you need to consider. As you might know, there is hot sake & cold sake as a category. Actually, there is normal temperature sake as well. Also, we can separate each category into more detailed ones, but I will talk about only hot & cold Sake in this article to make it simple.
We Japanese call cold Sake “Reisyu/冷酒” and call hot Sake “Atsukan/熱燗”. In fact, depending on the types of Sake (if you do not know the types, you can learn HERE first), the recommendation for temperature is different.
For Reisyu/冷酒, you should choose 純米大吟醸 (Junmai Daiginjo) or 純米吟醸 (Junmai Ginjo), which has richer flavor. The feature of Reisyu/冷酒 is its freshness and good for tasting flavor. From Donki, I highly recommend to drink Dassai/獺祭 after making it cold in a fridge. You can enjoy the fruity flavor more.
For Atsukan/熱燗, it is good for 純米酒/Junmaisyu, which has stronger rice flavor. You can enjoy the pure Sake/Rice taste from Atsukan/熱燗. Actually this is a tips to make cheaper Sake that has a low rice polishing rate more tasty. I personally think that heating Sake is especially good for the reasonable price of Sake in general. On the other hand, it is not suitable to 純米大吟醸 (Junmai Daiginjo) or 純米吟醸 (Junmai Ginjo) since it will destroy the flavor by making it hot.
When you make Atsukan/熱燗, I recommend you to refer to this video, which explains how to heat Sake at home. You can find an easy way to heat Sake.
Enjoy your drinking life!