Can I start a loyalty system with a physical card that gets stamped or punched and after some purchases give one for free with Loyverse?

Ok, so I sell drinks like Coke, water, etc. at a weekly market. I want to start a loyalty system with a physical card that gets stamped or punched and after say five paid drinks they get one free. The card will also have a barcode on the back unique to that customer. I also want to be able to track a customer's purchases so that I can check they haven't fraudulently punched the card themselves when they say they are due for their sixth and free drink. If I put the drinks in as Items, then I can't track the customers' purchases - only the type of drinks sold. If I input the customer as an Item, I can use their unique bar code to record their cumulative purchases (all drinks are the same value by the way). The problem is that I then lose the ability to inventories the stock. Has anyone got any thoughts on the best way to do this (if it is, in fact, possible) or do I just have to track one or the other? I had a look at the Loyverse loyalty option, but that doesn't seem to do what I want either.

First of all I really like your idea using the punching cards. Coming to your question, why don't you add both your customer and the items to the ticket? You can add the customer with price 0 - this way you will track the times he made a purchase. Then, adding also the items will solve your inventory problem. And actually, think of it, the Loyalty option could help you. You mentioned that every drink has same price. So lets say every drink costs 5$ - If the customer is buying 5 drinks he spends 25$ If you set the loyalty % as 20% for every purchase he will accumulate 1 point (out of 5) So after 5 purchases he accumulated 5 points which equal 5 $ that they can use tu purchase the next drink. What do you think?