First off....don't use soap on your snake! I hope you made sure the poor thing was very thoroughly rinsed off. It's possible the soap irritated him enough that he threw up whatever water he swallowed.

While I don't think tossing up excess water after a bath will have the same "regurge" affects that throwing up a rodent will....if I were in your shoes, I would give it at least 10-14 days before trying to feed anything, to make sure any residual soap is out of his system. Make sure he has LOTS of clean water to drink.