I recently had a pierced milk carton spill around 2 pints of milk into the rear footwell of my car. I have tried various things to get rid of the smell (pet urine remover, Dettol). It works for a while, but as soon as the carpet dries out again the smell comes back. Any other ideas for what I can try?
An enzymatic cleaner such as BioKleen Bac-Out should work, if you can apply it thoroughly, let it soak a while, and perhaps do it several times.
My buddy had a gallon jug shoot off the seat and explode. After multiple tries we gave up any in-vehicle cleaning.
Our cure was to strip out the carpet and padding down to the floor boards, clean the floor boards, replace the carpet padding and thoroughly wash out the carpet with various enzymatic substances and let it sun dry, testing for smell after each wash. It was a custom carpet that he thought worth the effort to save. Personally, I'd have just replaced the carpet as well.
Once milk gets into the carpet pad, it's nigh impossible to get rid of. You can try a lot of water and towels to try diluting out the milk remains, but it's a Sisyphean task.
The take away from this is never carry milk in the passenger compartment. Put it in the trunk in a box so it isn't free to move.