This isn't just plain water.

这不仅仅是淡水。

youdao

To reconstitute dried tomatoes, simmer in plain water until they are tender.

给干西红柿加水使其复原，放在清水里炖直到它们变嫩。

《柯林斯英汉双解大词典》

First boil in plain water for 20 seconds.

首先在白开水里煮20秒。

youdao

Okay, how little plain water was actually consumed.

好,所喝的白开水很少

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

To truly stay well hydrated, you likely have to drink more coconut water, than if you drink plain water.

FORBES: The Truth Behind The Coconut Water Craze

The bottom line is that most people who lightly exercise do not need sports drinks or even coconut water- plain water is just fine.

FORBES: The Truth Behind The Coconut Water Craze

While coconut water is low in calories, rich in potassium, and fat and cholesterol free, the evidence that it is actually better than plain water for simple hydration is unfortunately lacking.

FORBES: The Truth Behind The Coconut Water Craze