どう／いかが

日本はどうですか。

Nihon wa dō desu ka.

How do you find Japan?

Asking for an impression

コーヒーはいかがですか。

Kōhī wa ikaga desu ka.

Would you care for some coffee?

いかが is the polite どう, and also offers something

味はどうですか。

Aji wa dō desu ka.

How does it taste?

Asking after serving something you cooked