YOU SAID:
I can't sleep because of last night
INTO JAPANESE
昨夜のせいで眠れない。
BACK INTO ENGLISH
I couldn't sleep because of last night.
INTO JAPANESE
昨晩は眠れなかった。
BACK INTO ENGLISH
I couldn't sleep last night.
INTO JAPANESE
昨晩は眠れなかった。
BACK INTO ENGLISH
I couldn't sleep last night.
That didn't even make that much sense in English.