I would like to know how fizziness can be measured.
I don’t think I mean merely the gas content of a liquid, but perhaps that too. Maybe I mean the quality and quantity of the gas bubbles? Perhaps I even mean only the perceived fizziness of said liquid.
I will put it another way, is it possible (if so how) for me to determine in any empirical way whether or not (random example) Coke is fizzier than Pepsi?
addition to say:
I have already considered shaking each of my target liquids and capturing the expelled gas in a plastic bag or similar, but I am not entirely sure that is the most “scientific” way to go. The only other measure I have come up with to measure perceived fizziness is to dip my tounge in each glass, but that does not really fulfill my “hard core science” needs 
Your perception of fizziness will depend on the size, quantity and longevity of the bubbles. I’m not sure how you’d measure bubble sizes without some fancy equipment. You could measure their quantity and longevity by carefully pouring an ounce of coke/pepsi into a tall thin glass (a bud vase ?) shaking the hell out of it then measuring how far the foam rises in the glass, and how long it takes to disappear. Sensitivity of bubble formation to gentle shaking could also be measured this way.
Brewers and brewing scientists use the measurement of volumes of CO2 in solution to describe the carbonation level of a particular beer or type of beer. In other words, a 1 liter volume of beer with 1 cubic liter of CO2 dissolved in it would have 1 volume of CO2 worth of carbonation.
This is affected by the viscosity of the beer in question- obviously a very light lager(Bud) with 3 volumes is going to have a different type of carbonation than a imperial stout with the same level of carbonation. The lager will probably have less head and faster popping bubbles, while the stout will be nothing but bubbles and foam at that carbonation level.
And, some beers are carbonated using a mix of nitrogen and carbon dioxide- Guinness comes to mind. This gives the bubbles a different feel & behavior than CO2 bubbles.
So in reference to your first question, I don’t think it’s exactly possible to measure the quality of fizziness, but you can at least empirically measure the amount of gas in solution. I’d also guess that Coke and Pepsi are close enough in viscosity to where it’s not much of an issue.
Brewers and brewing scientists use the measurement of volumes of CO2 in solution to describe the carbonation level of a particular beer or type of beer. In other words, a 1 liter volume of beer with 1 cubic liter of CO2 dissolved in it would have 1 volume of CO2 worth of carbonation.
This is affected by the viscosity of the beer in question- obviously a very light lager(Bud) with 3 volumes is going to have a different type of carbonation than a imperial stout with the same level of carbonation. The lager will probably have less head and faster popping bubbles, while the stout will be nothing but bubbles and foam at that carbonation level.
And, some beers are carbonated using a mix of nitrogen and carbon dioxide- Guinness comes to mind. This gives the bubbles a different feel & behavior than CO2 bubbles.
So in reference to your first question, I don’t think it’s exactly possible to measure the quality of fizziness, but you can at least empirically measure the amount of gas in solution. I’d also guess that Coke and Pepsi are close enough in viscosity to where it’s not much of an issue.