I never cleaned my fake plants, but thats because I got them at a pet store. I guess, if you have time, just let them soak in water and rub each leaf with your fingers. Thats what I would have done if I had gotten them from Walmart or some place like that. Just a thought.
I would just rinse with warm water thoroughly, let dry, and use, whether I got it at WalMart or the pet store.