Here's how you can get 99 sunflower seeds in a few seconds:

1. Go to the "Tip-Top Fair" festival.
2. go to the "Nail the rythm" stand.
3. just slam on the A button when there's a red one and on the B button when there comes a blue one so don't follow the rythm just slam on it like you are doing the "barbell lift" game! or when you fish on hamtaro RR!

P.S. IT WORKS!