I know you are looking for different words, but truly, as a native speaker, I would use 'thanks'.  I would say 'thanks' rather than 'thank you' if I was wanting to be informal:

Thanks a lot.

Thanks, man.  (Only with someone you know well.)

Thanks, dude.  (Only with someone you know well.)

Thanks, bro.  (Only with someone you know well.)

You could also say, 'thanks' and add a fist bump or a pat on the back.