I offered them a bath the other day, and even though they were both very curious about it, they thought it was only for drinking. They must've thought: "why on Earth don't we get a food tray of this size?"
After a while, I thought that Frodo was beginning to see the fun in it. He dipped his head in the water and shook his feathers. Then, he put a foot in there. Then, Isla came to chase him off because she wants everything that he wants. Isla only drank a bit from the water and then flew off again. So much for bathing that day.
|Image © chorp on tumblr|
I believe it's a matter of patience. It's not a big deal if they don't want to bathe, because budgies can still keep their feathers clean and neat when they preen. If you want to, you could try to use a soft plant spray, as long as it has never had any chemicals in it. If your budgie doesn't like it, he will try to get away and keep his wings tight over his feathers. The important thing is not to force them. If you make your budgies wet against their will too often, they may start to hate you for it.
But don't worry: it's part of their instinct to take baths. Domesticated budgies just need some time to see the use of it. So no rush. I'm just going to put the bath there again next time and maybe they will try again.