Past Tense:
* The ship sank beneath the waves, taking its crew with it.
* The sun sank below the horizon, painting the sky in shades of orange and purple.
* My heart sank when I realized I had left my phone at home.
* The weight of the news sank in slowly.
Past Participle:
* The sank treasure was finally discovered after centuries of searching.
* The boat was sank by pirates.
* The argument sank any hopes of reconciliation.
As a Noun:
* The sank of the Titanic is a tragic reminder of human fallibility.
* The sank of the ship was blamed on a faulty rudder.
You can also use "sank" in more figurative ways:
* His spirit sank after the news of his friend's death.
* Her confidence sank as she struggled to keep up with the others.
The specific context of your sentence will determine the best way to use "sank."