United Kingdom, April 25 -- Kieran Culkin sleeps for three hours a night.

The 42-year-old actor is currently starring in a revival of 'Glengarry Glen Ross' on Broadway and though he intended to mimic the healthy habits of his former 'Succession' co-star Sarah Snook, who has transferred her one-woman show 'The Picture of Dorian Gray' from London's West End to New York, he admitted his pre- and post-performance lifestyle is very different.

Asking Sarah if she is "keeping up" her health for Variety's Actors on Actors, she told Kieran: "Yeah, I'm not drinking coffee."

He noted: "You did that in London. There was no alcohol."

She replied: "Yeah, and no coffee. If I have a coffee too late, I can't sleep after the show."

Kieran then admitte...