It just so happens while I was writing this she was spitting up
In my experience (and I have a lot of experience with stinky neck, having 4 kids were all pukers and spit up a lot) when you have stinky neck it needs to be cleaned at least once a day, if your kiddo spits up or throws up a lot then baby's neck needs to be cleaned up more often. A baby wipe, burp cloth, or wet wash rag will work just fine. There's no need for a complete bath every time you clean baby's neck just as long as you get all the goo and whatever else is growing in there.
Now this here is a shot of Carly's neck which is relatively clean for her. Thankfully she is spitting up less. But believe me when I first noticed Carly's stinky neck (because I forgot all about stinky neck) if was gross with curdled formula and other such nastiness. I am proud to say that Carly is no longer stinky! :)
Have you sniffed your loved ones neck lately?
Have a Great Day!