Question about CO2 production by yeast: glucose, fructose, and sucrose

I did a lab a few days ago, and hypothesized that monosaccharides produce more CO2 than disaccharides when yeast ferments.

The data resulting from the experiment was kind of confusing. I tested glucose, fructose, sucrose, and water. See the data attached.

Glucose is disturbingly close to sucrose in terms of CO2 production. Why? Shouldn't it be producing as much -- if not more -- CO2 than fructose?

Also, why does water produce CO2?

The probes used are fine and the experiment was controlled and consistent. The same amounts of yeast were used. The same amounts of carbohydrates were used. All of the sources were heated to 37.4 C before mixing in the yeast and sealing it all with the probe.

Thanks for any help you can give.