Oh and dont let them eat chocolate and cookies too.I can't edit my post so adding a bit here.
Budgies will also eat most fruits but won't take citrus. Apples, carrot, peaches, nectarines, watermelon, rock melon (cantelope) are readily taken.
If you have Australian native plants like bottle brush, gum trees or grevilias, you can cut branches from these plants and put them in the cage for the birds to chew on.
Let the birds fly around each day. Close the curtains or have some sort of fabric over the windows to stop the birds flying into the glass.