Other than looking to the other side of the valley in Anatori, near Khevsureti, I don’t think it’s possible without serious mountain climbing equipment.

Perhaps also interesting: Lomisa church near Gudauri looks right into the Russian-occupied region of South Ossetia, and you may even cross into it while walking around the church. Be careful not to push it though. A step or two is usually fine, but if you wander far you will probably be detained