We have all done it, we discover a baby bottle under the couch or forget our travel mug with half a latte in it in the cover over a hot weekend. And the smell of sour milk can be hard to get out of the bottle or mug. But here is how to do it!
Get a large plastic bowl or bucket, large enough that will allow you to submerge the mug/bottle (and lid!). Add 1-2 tablespoons of baking soda, then add enough hot water to fully cover the bottle. If needed, place sometime heavy on top to keep it submurged. Allow the bottle/mug to sit for 12-24 hours (the longer, the better!) Remove, rinse then wash in dishwasher or handwash with hot soapy water as normal.