https://www.rollitup.org/grow-room-design-setup/200112-simple-fermentation-diy-co2-producing.html
Check out this link. This is the right way to do it. With pics and the right recipe for a good fermentation mix. Use champagne yeast or brewers yeast if you can. Last longer brews stronger. The bubbler lets you know when to give the bubbler a shake to keep it brewing. I shake all of mine once a day.
And that hater that said it doesn't work is prob a diy snob who makes the cash slinging and has never been broke.
It works very well. The more bubblers you make the better it works. There is also a cheap gauge that you can buy to make sure its working (even though the bubbler tells you so). It is a large hypo syrnge (no needle) that you suck in the air around your plants. Crack the glass ends off of the gauges they provide, push the air through, and you have an accurate reading that you can use to prove to any of these doubters that it works.
Good luck