You shouldn't read in the sun.

你不应该在阳光下看书。

Please don't read in the sun.

请不要在太阳下读书。

Don't read in the sun, please.

请不要在太阳下看书。

It's bad to read in the sun.

在太阳底下看书对眼睛不好。

It hurts eyes to read in the sun.

在阳光下看书对眼睛有害。