In an appearance at New York's 92nd Street Y cultural center to promote her new book, Stewart told Bravo host Andy Cohen she saw some sloppy joints on her way to the event.
"I was driving here tonight ... and there was this stupid ice cream truck in front of me. 'Something Good Cream' or something. And we pulled up right next to it ... and a girl and a guy were smoking joints ... I said, 'Boy, those are sloppy joints,' " she said.
"Of course I know how to roll a joint," she said.
During the appearance to promote "Living the Good Long Life: A Practical Guide to Caring," Stewart also played a game in which she had to pick which of three celebrities she would prefer to "shag, marry or kill," The Hollywood Reporter said.
Between Donald Trump, Bill Gates and Mike Bloomberg, she said she would kill Trump since "ignore" isn't an option and she would marry Bloomberg, which left Gates as a shag.