Sure, here are the rewritten sentences:

25. Although he is strong, I'm not afraid of him.
→ Despite his strength, I'm not afraid of him.

26. Although she doesn't earn much money, she spends like a millionaire.
→ Despite not earning much money, she spends like a millionaire.

27. Tom will not pass the examination although he studies well.
→ In spite of studying well, Tom will not pass the examination.

28. He is still fat though he has been on a diet for 2 years.
→ In spite of being on a diet for 2 years, he is still fat.

29. Although Judy was severely disabled, she participated in many sports.
→ Despite being severely disabled, Judy participated in many sports.

30. She didn't eat much though she was hungry.
→ In spite of being hungry, she didn't eat much.