cheap co2

how can i make some cheap co2 i herd i can mix vigner and baking soda in milk jugs?

make it via fermentation. There are some How To's in the growFAQ. You basically mix a few cups of sugar with a gallon jug of water and then add a few tablespoons of yeast. Put a lid on the jug and poke a hole in it. Be careful because it may overflow during the first "rise". Check the growfaq for more precise details.