When glucose is taken into the cell, the fluids or solutions in the cell become more concentrated (due to the absorbed glucose) than the fluids outside the cell. When this happens, a natural process called osmosis takes place .
Osmosis is defined as the movement of molecules of a solvent (in this case water) through a semi-permeable membrane (in this case the cell membrane) from a less concentrated solution to a more concentrated one in a bid to to equalize the concentration on both sides of the membrane.
Water will therefore leave the less concentrated solution outside the cell, pass through the cell membrane and into the more concentrated solution.