There is a Czech company Filtermac ("Lokni") that doesn't even offer tap water, only filtered (so you don't get a comparison to the already safe tap?) Your options are:

• Install app, verify phone number, get
  • free 0.5 liters (2 glasses) per day at select stations (train stations, plus unis if you are a student)
  • access to subscriptions, the "unlimited" (still limited) tier is $8/mo I think
• Pay with credit card, about half of what bottled water costs

The startup says it's very successful. WTF? Tap water is already safe in my country so you can just pay $0.50 to access toilets (or jump the gate), many railway stations also have free taps.

Also, you need to keep the phone in a receptacle while the changing QR code on screen is being scanned during the bottle fillling (bring your own bottle or get a glass one shipped with a year of Premium). Tablets and laptops with Android emulators don't fit. You only need internet to sign up but the giant thing with an ad screen does not provide Wi-Fi.