If it actually tastes like a lake then it’s probably the ice. Ice machine bins are notorious for growing algae in the bottom and no business likes sanitizing the bin because that requires emptying the bin and therefore not having ice for a while. I’m also willing to bet that dunkin “does their own ice machine cleanings.” Which usually means that once it gets so crudded up that it stops working then they put it through a clean cycle so they can tell the repair tech that that they now have to call that they clean it. Ice machine manufacturers also don’t like to advertize that the built in cleaning cycles don’t actually remove the need to have them professionally cleaned; you only find that out if you read the service manual. Every 3-6 months you still need to take the whole thing apart to manually scrub the biological snot and limescale out of them.

Seems people started communicating with selfies so fucking weird