Why not use wifi? I’m using the TP-LINK nano router in client mode since my garage isn’t wired. It’s about 40 feet from the router. However you can get routers that will accept an external antenna to increase the range. It would get the opensprinkler on the network where you could access it. The other route is to bury cat 5. We did this at my dad’s place when we ran power and everything else to the new shop which was about 200 feet from the house.
Mark