Depends on the method of digestion. I am going to assume you mean after complex sugars have been broken down into the simple sugar glucose. At this point glucose can be broken down in two ways in a cell, depending on if the process is aerobic or anaerobic. Aerobic respiration, as it is called is when breakdown occurs with oxygen present. The end products of this are ATP and something I don't remember. If the breakdown is done without the presence of oxygen, it is not as efficent and it produces less ATP and lactic acid. Lactic acid is the stuff that creates that burning sensation in your muscles after they have been worked hard.