Due to environmental changes, the water concentration outside of a cell becomes lower than the water concentration inside of the cell. How would the cell most likely respond to maintain homeostasis?

Since the water concentration (also the water potential) is lower than the cell inside, the water will most likely flow from the cell out to the outside. This is because of osmosis, where the rule is water molecules will flow from a region of higher water potential to a region of lower water potential, through a semi permeable membrane (cell membrane).

When the cell looses water, depending its whether a animal or plant cell, if it's an animal cell, it'll shrink. If it's an plant cell, since there is the presence of the cell wall, the cell membrane will detach from the cell wall, and this phenomenon is called plasmolysis.