Good bowel preparation allows the doctor to clearly see
the whole lining of the colon. The procedure is then more
likely to be accurate and complete. If the bowel is not
completely clean and empty, the procedure may need to
be postponed or repeated, some complications may be
more likely to occur, and important findings, like polyps
and cancer, could be missed.

Clear fluids are any fluid that you can see through, examples are; Water, Clear soup (strained chicken broth), Jelly, Clear apple juice, Black tea or coffee, Sports drinks. Milk is NOT a clear fluid and you should not drink alcohol during your preparation