Account for upgrade is different to account in phone settings

My father-in-law had forgot his Apple ID on his iPhone. He had his friend enter his details to download some apps on to his phone. He's since reset his password and set his phone back to his own account (both the iTunes and iCloud are using his email address). The issue is, when he goes to upgrade some apps it's asking for the password for his friend's email account? How can we resolve this?