City transport company BKK should be distributing water at three busy points in the capital, Deák Ferenc tér, Széll Kálmán tér and Keleti station. Also on Deák Ferenc tér, you’ll find a water distribution trailer, from which you can refill your own bottle.
Together, Budapest water company Fővárosi Vízművek and FŐKERT public parks and gardens have expanded the number of existing drinking fountains. You can easily find their locations on this map on this Hungarian-only page.
The Közkutak site gives details across Hungary – you can download an Android here and an iOS version here. The map not only shows drinking fountains but also those shops and restaurants participating in the Refill – Fill again! project, in which anyone can fill up their water bottle for free.