Sorry Bailo, sand and glass is not the answer, but twas a good guess!

I assume plants/seedlings was wrong, so let me think...

I am best warm,
For warm I must be to make,
And come in many flavors,
which come from things that fall in harvest,
But I am not baked or made like a cake

Upon second thought, I believe the answer to your riddle just may be... Tea?