Tilde not returning home directory

After sudo command to change user, Tilde (~) not returning current user's home directory but returning previous login user's home directory. I needed to expand with echo ~USERNAME but I need to make echo ~ to keep compatibility existing apps.

user1@server1:-$ whoami
user1
user1@server1:-$ sudo -u user2 -s /bin/bash
user2@server1:-$ whoami
user2


user2@server1:- echo ~
/home/user1
user2@server1:-$ echo ~user2
/home/user2