Hi!
Whenever I try to fill any food bowl, it won't let me. It says 'can’t interact' as if it was an unusable object. I haven't downloaded any pets related cc, so I don't have a clue what may be causing it.

Is this a brand new food bowl or one that's been used? Often when they've been used, they get turned around and so entering build/buy mode and just turning them around might be all you need to do.
That said, you've discounted the possibility that it can't be CC because you haven't downloaded any pets CC - doesn't matter. CC can go wrong in any number of weird and magical ways. I loaded my game yesterday and it crashed after five minutes. I thought maybe it was a Uni walkby mod. Turned out to be a woodworking bench. I hadn't even touched it, it wasn't on the lot.

Yeah, you're actually right. CC can get crazy.
But it was a brand new bowl, so there's no chance that it got turned around.

Then what I would do, one by one, is - move the bowl so it's right in the middle of the floor, just in case.
If it still doesn't work: force an error on the bowl.
If it still doesn't work: buy a new bowl.
If it still doesn't work: buy a different bowl.
If it still doesn't work: go to another lot with a pet and try the bowl there.
If it still doesn't work: backup, pull CC, buy a bowl.
If it still doesn't work: give the pet up for adoption, try fixing the game tomorrow.

So I tried the first four things. I guess my only hope is to pull out some CC. Thank you!

Are you sure you didn't download the buyable pet food mod? You have to have a box of pet food on the lot to fill the bowl.

Yes, I'm a blind dumbass. I completely forgot about that mod, everything works fine now!