My Libby did this too!
I have had quite a few dogs over the years and NEVER had one that did it.
To tell the truth, I don't remember how I got her to stop other than giving her heck for it. I bet she did it for a couple months. It wasn't constant she didn't do it every day, but she did like my other dog's doo!
I have never given my dogs pineapple! Here it's something we have in the home all the time and they've been missing out. So people use it for training?
Good luck and get the toothbrush out!