Budgies cannot live on seed alone. Although in the wild, our diet mostly consists of seeds, well we're not wild budgies. ^^. Here are some vegetables, and fruits that you can supply us with

Fruits
Apples, oranges, bananas, cranberries, grapes, apricots, kiwi, strawberries, pears, tomatoes and melon.

Veggies

broccoli, celery, carrots, peas, corn, romain lettuce, bell peppers, cucumbers, beans(cooked), and eggplant

Convincing

When my owner first showed me vegetables and fruits, I ran away because they looked so disgusting. But then my owner ATE them infront of me, so I decided that they were not yucky after all. :D. I began to love broccli, then it got me hooked on bell peppers, and celery. Pretty soon, I loved vegetables more then anything! Well maybe not my toys but, I sure loved them!
A way you can teach your pets to eat healthy, is eating it in front of them. It makes it so much more fun and convincing. Also, try EVERY day. If you had to choose between pizza and a salad, you would go for the pizza, right? But if the pizza is gone, and then you see the salad, you would most likely get curious and nibble on the salad. You can do this with YOUR budgie. Just take away your seeds for about 20 minutes and put in the fruits and vegetables. MAKE SURE IT IS NOT LONGER THEN 20 MINUTES. Or else your feathered friend could die.

Pellets

It is important that your pet eats pellets. In a seed mix, your budgie can pick and choose what he wants to eat. This doesn't give him a variety. But Pellets are VERY good for your budgie, and supply a parakeets body with a great amount of nutrition, assuming that your pet eats produce also. If you budgie does not eat pellets, be sure to supply him with ENOUGH veggies and fruits DAILY

Cuttlebone

A cuttle bone is an item used to keep your budgie healthy and trim its beak. It does not matter if you use a mineral block or cuttle bone. Personally I use one that has both. In the middle it is a cuttle bone, and the edgings is a mineral block. Cuttlebones/Mineral blocks keep your budgies beak trimmed and gives it the essential calcium it needs. If your budgie rips up his cuttle bone too fast, consider a mineral block.

DON'T GIVE UP ON YOUR BUDGIES DIET! HIS LIFE DEPENDS ON IT!