This phenomenon happens due to the varying concentrations of the solution inside and outside the cells. This is also called the tonicity or the measure of the osmotic pressure gradients in the two solutions of a system. The two solutions mentioned are the solution inside the cells and the solution outside the cells. We call it Hypertonic if the solution outside the cells is more concentrated than the inside of the cell. We call it Hypotonic if the concentration is greater inside the cell. Isotonic is the term when the concentration of both the cell and the outside environment is equal.
In the case of the problem, there is a higher concentration of glucose outside the cells and therefore it is a hypertonic system. Consequently, the water molecules will travel from less concentrated to a more concentrated solution thus making the cells shrink or dehydrate and eventually die.