Take a gallon milk jug or some similar container. Fill it with water (not too close to the top)and a few cups of sugar, mix it up pretty well so you have some nice sweet sugar water now. Add a small packet of bakers yeast. Drill a small hole in the cap so you can run a small tube over your plants. The yeast will produce a good quantity of CO2 as they comsume the sugar. You will need to add a cup of sugar every few days to a week. Add it slowly, because the solution will foam up bad and may spill if you add it too fast.