被

被 expresses passive voice in Chinese.

In passive sentences, the object of an action becomes the subject of the sentence, and the "doer" of the action, which would have been the subject of the normal (active voice) sentence, becomes secondary and may or may not be mentioned in the pasive sentence.

被 is the most common way to crreate the passive verb form

• 男孩吃了热狗
  • active voice* "热狗" is the object of the verb "吃"

• 热狗被男孩吃了
  • "热狗" is now the subject and "男孩" is the doer

• 热狗被吃了
  • passive voice with the doer "男孩" completely omitted

Why use them

Indicate that one has been negatively affected

他被打了

Secondly, passive sentences shift emphasis from the action's doer to the one affected by that action.

• 你被公司炒鱿鱼了?
  • 炒鱿鱼 (coll. to be fired)

我的手机被偷了

How to use 被

Normal use of 被 has a few preconditions:

• The verb to be used with 被 needs an object (this becomes the new subject of the 被sentence) Verbs that take objects are called transitive verbs
• If you're going to state who the verb was done by (the doer), then the subject doing the original action must be known
• The verb can't be too simple (for example, a one-character verb like 吃). Put simply, the verb needs to come after the verb. That "something" can be a particle like 了, a complement, or sometimes even an additional object.

Subj. + 被 (+ Doer) + Verb + 了

Examples

被 sentences with a doer:

• 我被他骗了
• 他被警察抓了
• 他被父母骂了

• 我的车被撞了
• 他们做的坏事被发现了
• 文件被删了

咖啡被我喝

you need something AFTER the verb

The correct versions would be as follows

咖啡被我喝了

咖啡被我喝完了

他被打

Corrections...

他被打了 or 他被打伤了

Forming 被 sentences

Some examples:

他没有被S打伤

他没被S炒鱿鱼

他的想法不被S理解

"Question forms of 被 sentences"

You can make 被 sentences into questions in the usual three ways to form questions

With a question particle, question word, positive-negative verbs

那些书被借走了吗

他被谁打的？

你是不是被公司炒鱿鱼了

被 Sentences with Aspect particles

Sources used

https://resources.allsetlearning.com/chinese/grammar/Using"bei"sentences