* Coffee Cream: Cream is primarily composed of fat. Fats are non-polar molecules, while water is a polar molecule. Polar and non-polar substances don't mix well (think oil and water). The cold temperature makes the situation worse, as the molecules in cold water have less energy to interact with the fat molecules. This leads to the cream separating and forming a layer on top of the water.

* Sugar: Sugar (sucrose) is polar and can dissolve in water. However, the solubility of sugar decreases as the temperature of the water drops. In cold water, the sugar will dissolve more slowly, and you might even end up with a gritty mixture.

To make coffee cream and sugar dissolve better, you need warmer water. The increased temperature provides more energy for the molecules to interact and break down the bonds holding the substances together.