Here are the rewritten sentences using "used to":

1. I used to drink coffee in the morning.
2. She used to travel to different countries frequently.
3. We used to celebrate birthdays with a big party.
4. He used to play the piano as a child.
5. They used to go camping during the summer.
6. I used to watch cartoons every Saturday morning.
7. I used to go to the gym every day.
8. They used to watch movies every Friday night.
9. He used to go for long runs in the park regularly.
10. They used to spend hours reading books in the library.