One of the best ways of generating sales quickly is to run a time limited promotion. A typical format would be
“Hurry! Sale must end Saturday.”
Offers like this tend to generate a strong response but they need managing. Apart from anything else you need to make sure that you take down the offer when it ends.
If your QR Code continues to generate traffic after the offer has ended you shouldn’t waste it though. Instead consider providing a sign up form that lets people join an email alerting list that will tell them about future offers.
That way they go away less disappointed and you get their contact details which lets you market to them in the future.
Never waste your web traffic!