Bumps buddy here you go hope it helps a bit.
"Small and simple
For those of you running smaller systems such as cupboard, closet or ?box? systems, there is a simple CO2 system that is easy to make and use. This system uses water, sugar and yeast mixed together in a jug, bottle or jar. I like to use one-gallon plastic jugs due to their size and availability.
Put about five or six cups of sugar in a clean one-gallon plastic jug. To this add about a half gallon of water. Mix until the sugar is dissolved and add a little bit of active yeast. Poke a small hole in the lid and replace it on top of the jug. Once a day, or as often as possible, shake the jug to thoroughly mix the contents. In a day or two the yeast will begin to grow and CO2 gas will be a by-product in the jug.
Once the yeast begins to grow, the shaking of the contents will produce a gaseous eruption through the hole in the lid. On its own, the device will slowly produce CO2 as long as there is enough sugar in the mix and the yeast stays active. The daily shaking stimulates the mix to produce a surge of CO2 gas. Therefore, the more times the jug is shaken, the more surges of CO2 that will erupt into the room. The mix will need to be changed or refreshed every two to three weeks. I have found this system to be more than adequate and perfectly safe for smaller grow spaces (twenty square feet or less). It is also very inexpensive to configure and maintain."
Here's the whole article about it
CO2 for you