Yes, you are able to force redeem currency from a guest. You can head to the guest's account and to the Force Redemption tab. In this tab, there is a field for 'Requested punches'. This is where you will enter the amount in the currency you wish to force redeem.
This will make an entry in the guest Timeline as seen below.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)