If we're simply filling up the balloons without stopping to see which one would pop first, then the one with hot water will likely pop first .

The high temperature of the water will help expand and thin out the walls of the balloon, and when the balloon expands past its capacity to hold itself together, it will pop. However, if we put the same amount of each of the liquids into three of the same type of balloons and tie off the balloons, we may need to consider how hot the water is and how much gas the soda has, because with the balloons tied off, the water vapor from the hot water and the carbon dioxide from the soda would push on the walls of the balloons.

The hotter the water, the more water vapor; the more gas the soda has, the more force it can exert on the walls of the balloon from the inside; which one of the these balloons pops first will depend on whether the water is hot enough or the soda has a large enough volume of gas. The one with cold water would still pop last.

It probably depends on the rubber that makes up the balloon. Maybe you should do an experiment and find out. Then you can tell us!

This is a tricky question. Liquids behave very differently than gases. A gas is compressible meaning that the volume will change as a response to pressure (and temperature). Because hot air expands, if the balloon was filled with air, it would increase the pressure inside the balloon relative to a balloon filled with cold air.

However, liquids unlike gases are mostly incompressible, meaning they don’t change volume very much with pressure or temperature. The density of hot water is only very slightly less than the density of cold water and won’t make any difference in terms of popping a balloon filled with water. Also, the density of soda (sugar+water) is similar that of pure water, so all three balloons should behave identically.

In a balloon filled with liquid the difference in pressure between the inside and outside of the balloon is balanced by the tension on the latex balloon. As the balloon stretches to accommodate the volume of the liquid, eventually the strain becomes high enough that the balloon breaks.