YOU SAID:

you can't make him drink.

INTO JAPANESE

彼を飲ませることはできません。

BACK INTO ENGLISH

I can not let him drink.

INTO JAPANESE

私は彼に飲み込ませることはできません。

BACK INTO ENGLISH

I can not let him swallow.

INTO JAPANESE

私は彼が飲み込ませることはできません。

BACK INTO ENGLISH

I can not let him swallow.