There are several stages to this deal.
1) Go to the link and add a can of Jack Daniels and Ginger Beer (https://bws.com.au/product/744743/jack-daniels-tennessee-whi...)
2) Go to the craft beer section, select any single craft beer, and add to cart. Although the 'Mix and Match' 25% off discount is meant to apply to 8 or more craft beers, due to poor web design it will apply the discount to the single beer.
3) Complete the order, and as many repeat orders as you like, so long as the store has enough stock. I was able to place 16 such orders at one store.
To maximise value, I selected cheaper craft beers (there are some good ones on clearance already, but this will vary depending on store) and generally placed orders around $2.50-$4.00 depending on the beer.
Note: due to the low value of the order you'll get a 'security check' SMS, and in some cases, the store might ring to check the order is correct, but otherwise they should honour it.
UPDATE: Looks like the 25% off glitch is gone, but you can still find cheap single craft beers to pair the freebie with here (courtesy of user 'houseishouse': https://bws.com.au/beer/craft-beer?filters=price($0-$4)