Take a can of diet coke and a can of regular coke, both cans are exactly the same in size and dimension, they also contain the same volume of liquid. In a simple home experiment or as a party trick place them both in water - which one do you think will float and which one will sink?
You will find that the can of Diet Coke floats and the regular Coke sinks. But what is the reason behind it?
Turns out it's just basic Physics. Remember Archimedes, architect of the Archimedes' Principle, who allegedly jumped out of his bathtub, butt naked and ran through the streets shouting, "Eureka!"
Archimedes discovered that if a solid lighter than a fluid is forcibly immersed in it, the solid will be driven upwards by a force equal to the difference between its weight and the weight of the fluid displaced.
A can of regular coke contains 39 grams of sugar whereas a can of diet coke contains 125 milligrams of sweetener. This means that a can of regular coke is more dense than water, so it sinks whereas a can of diet coke is less dense than water, so it floats.