YOU SAID:

lead a horse to water but can't make him drink

INTO JAPANESE

馬を水の所まで連れていっても水を飲ませることはできない。

BACK INTO ENGLISH

You can lead a horse to water, but you cannot make him drink. [Proverb]

INTO JAPANESE

馬を水際まで連れて行くことはできても、水を飲ませることはできない。

BACK INTO ENGLISH

You can lead a horse to water, but you cannot make him drink. [Proverb]