Unflavored sake is acceptable without Hashgacha. Flavored sake (e.g., Coconut Sake) and sake which states on the label that it was aged in wine casks require Hashgacha. Nevertheless, due to potential Kashrus concerns, it is preferable to only consume premium sake labeled as Honjozo, Ginjo or Daiginjo.

Pas Yisroel during Aseres Yimei Teshuva
אלול — Guidance for Aseres Yimei Teshuva: Pas Akum, Pas Yisroel, and Rosh Hashana By Rabbi Eliezer Eidlitz Main Ideas During Aseres Yimei Teshuva, the