Answer:
If I drink, I die. If I eat, I am fine. What am I?
Weight in my belly trees on my back nails in my ribs feet I do lack.
I am full of holes but still holds water.
When it comes to me you go on red and stop on green.
What can be as big as an elephant but weighs nothing?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.