USSR did that quite a few times. They'll invalidate existing bills and you would only be able to exchange a few of those.

Do this enough times and people will rightfully call the local currency "wooden", and switch to USD for any large transactions.

https://en.wikipedia.org/wiki/Monetary_reform_in_the_Soviet_...

Rouble also became worthless in the following years, Venezuela-style. Accompanied by Venezuela-like poverty.