It looks like HTC One M8 owners on Sprint have a fluffy sweet treat to look forward to, as the Marshmallow update should be headed out to the device imminently. That's according to HTC's Mo Versi, who says the company just received technical approval on the update, and the over-the-air-update will start tonight, January 29.
Sprint HTC One M8 / M8 HK Owners! Great news, we have received technical approval on the Marshmallow OS update! OTA will start tonight! Thx!— Mo Versi (@moversi) January 29, 2016
This would make Sprint's second update of the day for an HTC smartphone, as the One A9 just began receiving its Android 6.0.1 update as well. In any case, if you have an HTC One M8 on Sprint, you can expect to see the update hit soon.
Source: Mo Versi (Twitter)