Answer:
I am Invisible Man's drink at snack time
Part carbon part water I am poison to the fishes. Many falsely claim my name I am the pause that refreshes.
Brown I am and much admired; many horses have I tried; tire a horse and worry a man; tell me this riddle if you can.
I have feathers that help me fly; with head and body but I'm not alive. Very skinny and a fixed length how far I go depends on your strength.
I begin your sentences.
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard. Who am I?