给我一杯开水就好，谢谢。

Gěi wǒ yì bēi kāishuǐ jiù hǎo, xièxie.

Just a glass of hot water, please—thank you.

服务员，我想要一杯开水。

Fúwùyuán, wǒ xiǎng yào yì bēi kāishuǐ.

Waiter, I’d like a glass of hot water.

来，喝一点开水吧。

Lái, hē yìdiǎn kāishuǐ ba.

Here, have some hot water.