Hop water is dead simple. Hops cold steeped into tea for like 18 hours then add citric acid to bring the ph down and make it stable.
The only challenge is that is flat. If you have a kegerator you can put it in a keg under pressure and it will be carbonated in a day or so.
The keg and co2 system is a one time cost I'd already paid. The ongoing cost is crazy cheap compared to beer. Like 5 dollars a keg as I recall.