Vomiting is defined as the forceful ejection of the stomach contents up the esophagus and through the mouth.
Due to a very tight sphincter in their esophagus and the position of their stomach, it is impossible for rabbits to vomit. As a result, there is no reason for rabbits to be fasted before a surgery.
However, rabbits can very rarely regurgitate fluid or partially ingested material that has never reached the stomach. 
- Rabbit Meadows, Regurgitating Rabbits
- Drs. Foster & Smith. (n.d). The Difference Between Vomiting & Regurgitation. Retrieved 15 Mar 2017 from http://www.peteducation.com/article.cfm?c=21+1276&aid=1054
- The Rabbit Doctor. (2015). Facebook post. Retrieved 15 Mar 2017 from https://www.facebook.com/Therabbitdoctors/photos/a.1465023073717969/1632269380326670/?type=3