That bad smell in the refrigerator...

Did something drip? Milk or other item?
Spoiled meat?

I had a (commercially) fresh salsa in a plastic container start to go bad one time--I think it started to ferment and the change in pressure popped the lid open a little and all I could smell every time I opened the fridge was a garlic smell.

I find the culprit is usually in the veggie drawer, too.

lunchmeat or veggies

It’s usually black beans for us.

It's always some sort of veggie I've forgotten about ... it is now liquid and gross   

Hello box of baking soda   

This is what I was going to say.  Under it or behind it.

Last time this happened it was half a Cucumber hiding at the back of the salad drawer. I put my fingers straight into the mush  and then had to take a few minutes to compose myself before cleaning the drawer out..

Broccoli even if it doesn't look like disgusting mess it smells first.

I don't recall anything in a closed container giving off a smell no matter how moldy or puffed up the lid might be, so would go to the produce drawer(s) first.

My most common offenders are a rotten cutie in the middle of any otherwise fresh looking bag or melting greens (spinach, lettuce, etc.). Good luck!

Produce I usually in mine. Often some rotting broccoli or other veggies.

Broccoli. Always.

that.

My last stinky was a Cutie orange that somehow jumped out of the mesh bag and rolled behind the produce drawer.