This is one of my favourite types of enrichment/foraging toys for birds; branches, shrubs or whole plants of any kind of small, healthy, and bird-safe fruit or berry. (Pictured: Bilberries and Rowan berries.)
It’s easy, my birds love it, it involves a behaviour they would have used in the wild, it’s still fun when there’s no food left (most of my birds love picking the leaves apart afterwards), and, since I can just collect it from my backyard, it’s also free! Yay! 

Make sure all of what you’re using is actually bird safe (like for example, tomatoes are fine, but the actual plant is toxic, so don’t go picking any tomato vines!), and that it hasn’t been treated with any pesticides.
I usually run the whole thing under hot water for a while before hanging it up for the birds, and it’s also good to freeze it overnight to make sure there aren’t any weird things in there before you offer it to your pets.