If you are using the pass password manager, you can use the module passwordstore, which makes this very easy.
Let's say you saved your user's sudo password in pass as
Server1/User
Then you can use the decrypted value like so
{{ lookup('community.general.passwordstore', 'Server1/User')}}"
I use it in my inventory:
---
servers:
hosts:
server1:
ansible_become_pass: "{{ lookup('community.general.passwordstore', 'Server1/User')}}"
Note that you should be running gpg-agent so that you won't see a pinentry prompt every time a 'become' task is run.