It's for extinguishing oil well fires, owned and developed by MOL, the Hungarian oil conglomerate. It was used in Kuwait after the Kuwait-Iraq war, here is a video of it in action: https://www.youtube.com/watch?v=uyGDxglTVgA

It's still in use and maintained, the base was replaced with newer tank recently, as it was hard to find replacement parts for such an old model.

Video from some years ago, timestamped, there is a lot of Hungarian narration before that point: https://youtu.be/YYF8YQ7pLng?feature=shared&t=494

Good article in English about this beast, with a lot more images: https://www.autoevolution.com/news/a-firefighter-s-dream-meet-big-wind-a-tank-with-jet-engines-that-s-a-fire-truck-185011.html#