Some bezoars, like lactobezoars, can resolve quite easily often with intravenous fluids.  Trichobezoars often require surgery.  Phytobezoars can dissolve with  diet coke and cellulase (Gastroenterol Hepatol 2012; 8: 770-72).

A phytobezoar, which is the most common type, is composed of indigestible fruit and vegetable fibers and occur in the setting of impaired gastric motility.  In the three cases presented, the combination of diet coke and an over-the-counter cellulase (Enzymedica Digest Gold) which contains 3000 units of cellulase per capsule was successful at dissolution of the phytobezoars over a 6-8 week period.

The role of the diet coke is less certain.  The sodium bicarbonate in sodas and the penetration of carbon dioxide bubbles may have facilitated dissolution.  Additionally, the acidic pH (2.6) of Coca-Cola along with the phosphoric and carbonic acids may have been beneficial.  While Coca-Cola and Diet Coke have the same potential mechanism of action, Diet Coke is easier to administer in diabetic patients.

Additional references:

• -JPGN 2010; 50: 108.  Consider N-acetylcysteine to dissolve persistent lactobezoar.
• Bezoar – Wikipedia, the free encyclopedia
• Images for bezoar– Report images
• Bezoar – Harry Potter Wiki  While it may be helpful in Harry Potter, if your best friend is poisoned, I would not recommend shoving a bezoar down their throat.