I have been asked a few times recently in regards to getting tough stubborn water stains and deposits off of glass. I even had a bet with a friend I could remove some stains she insisted were not removable.
Now before you go full speed forward ALWAYS test the item in an inconspicuous place.My little trick in my bag is silver cleaner. It is abrasive but fine enough not to scratch the glass. I have successfully used it on clear and cobalt glass. My personal favorite is the paste type. You put a little on and rub with a microfiber cloth until the paste is gone and your glass sparkles. Weiman's Glass Cook Top cleaner and polish works well also.
With that being said never, never, never use it on glass that has been coated or painted. It will remove the paint or finish.
Helpful handy tip from The Other Alley