There aren't really any 'endings'. You can only get sex scenes and a victory scene for completing all of the nights. You can get all the sex scenes by dying to the girls (including golden freddy) and beating 4/20 mode.
Viewing post in (18+) Five Nights at FuzzBoob's: Definitive Edition comments
The other easter eggs are only images on cams, but don't give you sex scenes except for the donut one. The only other one I know, is the golden freddy easter egg. You have to go on cam 3 (closet) repeatedly, until the poster on the wall changes to have golden freddy's face on it. Clcik on the poster. After that, she'll pop up on your desk, and all you have to do is let her jumpscare you.
Sometimes it happens randomly, Golden freddy appears on your desk even if you haven't clicked on the poster on cam 3. If you want to get rid of her, just quickly go to cam three again, before she jumpscares you, and she'll be gone.
(Can't help with night 6, because I haven't gotten that far yet, sorry)
You have to click on the poster when it changes. If you notice, when you go back to cam 3 repeatedly, the poster on the wall changes. You just have to wait for it to change to Golden's freddy's face and then it changes. If you want the other golden freddy scenee, you have to set the custom night's difficulty to 6969, and she jumpscares you.