No, he has to drink the whole potion. Every last drop.
7 seconds sound clip from the Hercules movie soundboard.
You can hear this line at 00:12:01 in the Blu-ray version of the movie.
Quote context
[...]
- Just hang onto the kid, Panic.
- Hurry! Let's just kill the kid and get it over with, okay?
- Here you go, kid. A little Grecian formula.
- Look at that! He's changing.
- No, he has to drink the whole potion. Every last drop.
[...]