I did that with three straws coming out of a 1 ½ litre coke bottle. Just a load of work for what seems to be not much.

1/4 teaspoon of yeast and 2 cups of sugar will result in CO2 production for about 4 to 5 weeks.
I vehemently disagree. You can check whether there is CO2 coming out of the tube by putting the tube into a jar of water and observing the bubbles. I've done it loads of times, and after 2-3 days there are no bubbles, unless you shake it. If you shake it after that period of time, you still only get CO2 production for a couple of minutes.

Also, make sure you're changing the water often because it builds up alcohol, which kills the yeast after a while.

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