Have just passed through the airport both ways (departures and arrivals) – there is no water fountain in either Schengen or non-Schengen areas. The airport is tiny – just one shop (duty-free) that sells water in all sizes – €1.90 for 1.5L
maybe there was a water fountain at some point that has since been removed – everyone around had bought water from the shop too
#plasticfree @aena @aena.es