I bought golden cypress from nursery and didn't get time to plant them nor water them.. After 3 days I planted them but it's needles were brittle?? What should be done to cure them?? I water them regularly depending on the moisture content of the soil
Brittle needles doesn't sound good. You can scrape off a little bark from a couple branches and see if there is green underneath. If so, they are still alive. I would not think only three days without water would be enough to kill them unless they were very small.
Continue to water when the soil is dry and see if the foliage gets a little more pliable.