Did the smell of it make you want to vomit? Or was it just a little stinky? Regurges are THE nastiest, stinkiest things I've ever smelled, and I've helped descent skunks! If it was just a little stinky, it might have been poo, but since it was sitting in the water, it disintegrated. There is usually a lot of fur and sometimes undigested bone in poo.

The drinking water and eating it backward would not cause a regurge. Improper temps and stress could though. Tell use exact temperatures, humidty, describe set-up, etc. and let us know what you're using to measure with. Analog thermometers can sometimes be way off, sometimes 10 degrees or more.

You should probably wait a while before feeding again, 3-4 weeks, depending on the age of the snake and body condition (how big is he?), and start with a small prey item.