This is straightening the back.
3 seconds sound clip from the Kung Fu Of 8 Drunkards movie soundboard.
You can hear this line at 00:14:27.433 in the Blu-ray version of the movie.
Quote context
[...]
- Cousin, how did you get it? Did you learn it?
- Why don't you show me right now how good your Kung Fu is.
- Now watch me. That's called the toast to butter.
- This is straightening the back.
- This is the drunk staggering.
- This is called taking a drink.
- So you learned Kung Fu... you can take on 20 guys at once, can you?
[...]