How to clean a toaster from inside

Bleach is your best bet. Scrub it with a long-handled scrub brush and either liquid bleach or Ajax and water. Let it soak a bit before rinsing it out. Since it's stainless steel, the bleach won't do it any harm and will kill off any organics growing on it.

In my experience, the pink stuff is a mold, not flouride.

I have found that a tablespoon of Oxy Clean followed by boiling water will remove even the harshest stains inside a vacuum bottle. Fill it to the brim (it will bubble and overflow, so do it in a sink), let it sit for a bit, then rinse very very well, and you will be amazed, I promise. I do this periodically to remove the coffee stains inside our steel thermos flask. [Edited for typos]