Sure! Here are the sentences you requested with the nouns replaced by direct object pronouns:
-
They want the book.
- Lo quieren. (Replaces "the book" with "lo")
-
You need us.
- Nos necesitas. (Replaces "us" directly)
-
He buys the sandwiches.
- Los compra. (Replaces "the sandwiches" with "los")
-
I love you.
- Te amo. (Replaces "you" directly)
-
We eat the apples.
- Las comemos. (Replaces "the apples" with "las")
Feel free to ask if you need further assistance!