yeast??

what does a bottles of yeast with sugar and water do or what does it contribute to the plant

yeast consumes the sugar producing CO2 which is ensential for plant life. however i think that stuff is a waist of time. most growers frequent there plants 1-many times a day. a human exhale has about 1500ppm of c02. so it really isnt needed for a small grow. bigger well thats a different story then worry about co2