He recited the whole poem in one breath.

他一口气背出了整篇诗。

Heidi had said all this in one breath, she was so eager.

海蒂一口气说完了这一切，她是如此的渴望。

In one breath? That's not true.

一口气？谁说的？

I can swim about 100 meters (in one breath).

英文翻译：我能一口气游一百米左右。

As the saying goes in one breath to eat not a fat.

俗话说一口气吃不成胖子。