I had a rough few cycles recently, had very reduced run times. Screen on time was below 8h (which wasn't typical of my use). I noticed YouTube was draining significantly high CPU resources over a short period, so much so the device was warm to the touch. I saw at least 20% to 30% battery drain within an hour. My guess is that when I signed up for the free YouTube Premium upgrade, it added the background features which seems to have had some detrimental effects. I disabled the background play and downloads I had and it seems to have settled. I had a similar experience from using the Google One app (although it may be Google Photos as the culprit), but this was more to do with the backup kicking in which I believe I never set before. Other than these issues, my battery life on my S25 Ultra has settled again.
TL:DR if you notice a sudden battery drain in your device, do check the Google apps, YouTube or Google photos, both seem to have bugs or quirks that can drastically kill battery life, which may be related to backup or background play.
