Final answer:
To increase the energy of a glass of water, the water should be boiled, as this adds energy to the water by increasing its temperature and its entropy.
Step-by-step explanation:
To increase the energy of a glass of water, you should boil the water. Boiling the water will give its molecules enough energy to pull apart from one another, transitioning from a liquid to a gaseous state which increases the system's entropy. In this process, energy is absorbed to break the intermolecular forces holding the water molecules together, leading to an increase in both temperature and energy content.
Other options, such as mixing or drinking the water do not add energy to the water itself. Freezing the water would in fact remove energy from the water, as the process of freezing releases heat to the surroundings when water transitions from liquid to solid form. Therefore, to achieve an increase in energy, boiling is the effective method.