This is something I've actually thought about because... I wanted to

I honestly can't think of anything for Freddy rn

Bonnie would listen to Mother Mother and his brain is on a constant Hayloft loop. Idk, he just gives me that vibe. It may or may not have something to do with that dream I had.

Chica would probably like Doja Cat because I can't think of anything else also Doja Cat songs are bangers I don't care what you people think

Foxy's favorite band would be Flogging Molly because it sounds like some kind of freak hybrid of punk and sea shanties and he would absolutely be into that

Golden Freddy likes Queen I would think

Spring Bonnie would probably just listen to stuff that was popular in the late 70's and early 80's because that's what they're familiar with

Puppet almost exclusively listens to music box covers (Also according to the Popgoes arc is favorite song is Pop Goes the Weasel and since he wrote that entire arc I think that's accurate)

I'd think BB would be pretty flexible, but he won't listen to Kidz Bop because he still has taste

JJ listens to alt, mainly Ghost and Pals (I refer to them as Ghost and Pals instead of just GHOST as to not get them confused with Ghost, the Swedish metal band)

Toy Freddy probably doesn't care much for music and just listens to Ebooks and such, but when he did it would probably be classical

Toy Bonnie... I have no idea with this guy I'll get back to him at some point

Toy Chica is a Taylor Swift Stan because of course she is

Mangle would like Maretu and TV Girl because she's cool like that

I haven't listened to much Mindless Self Indulgence but for some reason I feel like Springtrap would like it

Coffee would listen to Lofi beats because it would help him chill tf out

Finally I think Candy would listen to Vocaloid because he knows who Hatsune Miku is and he also just... seems like the type of person who would like Vocaloid (I can confirm this as a person who also likes Vocaloid)

I know I left some out but this is all I could think of for now