First off I'd say that there are many different recipes for this. It's also something that is rather forgiving. Cut everything in half try it out. generally more sugar or more yeast will mean higher output for a shorter amount of time.
Personally I use 1tbls of molasses, 1 cup of sugar, 1tsp baking soda, and a bit of yeast. I add more yest now then i did originally because i think my yest is getting old.
When i started i was scared to use a 2L bottle on a 10g tank, so i used 1L. All i did was cut the recipe to .75-1cup sugar, less than 1/4 teaspoon of yeast and pinch of baking soda (good with soft/acidic tap water). Just make sure you hydrate yeast prior to adding it to the mix. That way you will get faster/better results.