Will coke or diet coke sink in ice water, what about regular temperature water?

Answer 1

Regular Coke will sink and Diet Coke will float. Regular Coke is filled with tons of sugar which makes it more dense than water. Diet Coke has less things added so it is less dense than water - or just about the same density as water. This is a demo I do each year when I teach density.

Answer 2

Soft drinks are mostly water, and have a specific gravity (density relative to water) very close to 1.

Water expands when it freezes, and ice is much less dense than water, but just before freezing, there is a slight increase in density, so it's very difficult to make a call on the first question. However, if we assume equal measures by volume of chilled water, ice, and coke, I would make the educated guess that the soft drink would be more dense and therefore sink.

In room-temperature water, the soft drink would proboly sink as well because it is a mixture of water and various hydrocarbons (heavier than water).

However, in both cases, it would be difficult to determine experimentally because the two substances would mix easily, since they are both polar and have similar molecular weight / size.