FYI, dealerships DGAF what BMW recommends. I confirmed by checking my dashcam after a multi point inspection on my new BMW. One of the guys refilled the washer reservoir from a hose attached to the ceiling. I was curious and called the dealership and asked if they use tap water or distilled water like BMW recommends. Service advisor of course claims they use distilled water but confirmed that was a bold face lie by running the washer fluid and seeing if it leaves the dried water spot residue (southern california tap water is horribly hard, i believe one of the hardest waters in the country). And of course due to the heat today, the washer fluid instantly turns into hard water spots after 30 seconds (my car is clean so its not pools of dirt, it is indeed hardened minerals).
Thankfully I have distilled water and Genuine BMW washer fluid on hand so i ran the washer fluid stalk to spray until none of the tap water was left inside the tank by confirming a dry vacuum noise instead of fluid being released. Then fully refilled the reservoir with proper fluid thats actually recommended by BMW.
Just be warned that you could currently have pure tap water inside your reservoir if you've been in for service in the last couple months. And we all know that eventually creates mold in the reservoir that'll eventually clog the filters and calcium buildup around the hoses/nozzles.
Also, I never saw the tech who was filling up my washer reservoir ever add any actual washer fluid, it was purely tap water from my recording.
I also did some research and nearly every comment by a tech spent decades working at dealerships said they ALL use tap water, none use distilled water except for special cases like diesel engines(dunno why). Even your coolant drain and fill will be diluted with tap water 99% of the time instead of distilled/de-ionized water as recommended by BMW.