At which temperature would a can of soda be most fizzy when it is opened?

at higher temperatures.
Justification:

1) Soda have CO₂ dissolved. Carbonation consists on that: dissolving CO₂ into water, leading to carbonated water.

2) The solution of a gas into a liquid is inversely related to the temperature: the lower the temperature the more gas gets dissolved.
So, in the manufacturing of soda, the CO₂ is added in cool water in a cool environment.

3) So, the higher the temperature after the soda is delivered, the more gas will be liberated when you open the can.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.