you just answered your question by yourself
Go ahead and spawn your objects offscreen and let them fall down (i.e. using the bullet behavior)
and compare if they either hit the ground or went past a certain y coordinate.
Simple start could be:
- Angle 90 degrees
- Active on start: true
Every X Seconds:
- Create Object (Food) at (random(0, WindowWidth) on Layer XYZ
Food on collision with ground (or when y value = ground y):
If you're fancy, add sine behavior as well.
Hope that helped you somehow