I always wake up once or twice in the middle of the night to go to the toilet (bathroom)
wake up in the middle of the night / wake up at night
「寝てる時、途中で目が覚めて必ず1、2回はトイレに行く」＝ I always wake up once or twice in the middle of the night to go to the toilet (bathroom)
※イギリス英語では「toilet」を使っても大丈夫ですがアメリカ英語では「bathroom」の方が丁寧です（笑）
「夜中途中で目が覚める」＝ wake up in the middle of the night / wake up at night
Every night I wake up at least once to go to the bathroom.
I always have to go to the bathroom at least once in the middle of the night.
I always have to get up in the middle of the night to use the bathroom at least once.
結構似ていると思いますが、言い方いくつか紹介します。
① Every night I wake up at least once to go to the bathroom.
Every night＝毎晩
I wake up＝起きます
at least once＝１回以上（少なくとも１回）
to go to the bathroom＝トイレに行くために
② I always have to go to the bathroom at least once in the middle of the night.
always＝いつも
have to go＝行かないといけません
to the bathroom＝トイレへ
at least once＝１回以上（少なくとも１回）
in the middle of the night＝夜の途中に・深夜に
③ I always have to get up in the middle of the night to use the bathroom at least once.
always＝いつも
have to get up＝起きないといけません
in the middle of the night＝夜の途中に・深夜に
to use the bathroom＝トイレを使うために
at least once＝１回以上（少なくとも１回）
イギリス 
アメリカ合衆国 
