You can make a coupon work only when certain products are in the cart, and choose how many of them the customer must buy. For example: "Buy 6 bottles of our Shiraz and get a bottle of Rosé free", or "10% off when you buy 3 or more Riesling".
Three settings on the coupon control this:
Required Products in Order: the products that must be in the cart for the coupon to work.
Minimum Required Product Quantity: how many of those required products the cart must have. It appears once you've chosen required products, and starts at 1.
Applies To Products: the products that get the discount. Same as Required Products (the default) discounts the required products. Different Selection discounts other products, for example a free Rosé when the customer buys Shiraz.
By default a coupon doesn't require any products and applies to everything in the cart.
Steps
Go to Settings > Coupons and open the coupon, or click + Add Coupon.
Next to Required Products in Order, click Edit product preference. The Select Required Products for Coupon window opens.
For a new coupon, every product is ticked. Untick All Products, then tick the products the order must include. You can tick a whole group, such as All Wines or All Mixes, or single products.
Click Set Products. The form shows what's required, for example Requires 1 Wine.
In Minimum Required Product Quantity, enter how many of the required products the cart must have, for example 6. It must be 1 or more.
In Applies To Products, leave Same as Required Products to discount the required products. Or choose Different Selection, click its Edit product preference, tick the products to discount and click Set Products.
Set the Discount type, any shipping discount and the rest of the coupon, then click Save.
How Minimum Required Product Quantity counts
It only counts the required products. Other products in the cart don't count towards it.
It adds up all the required products together. If Shiraz, Riesling and Rosé are all required and the minimum is 3, one of each is enough.
A mixed pack counts as the bottles in it. One mixed six pack counts as 6.
Required products don't have to be wine. You can require merchandise, such as a T-shirt.
Using it with Minimum Order Bottle Quantity
Minimum Order Bottle Quantity counts every bottle in the cart. Use both settings together for offers like "buy any 12 bottles, including at least 6 Shiraz": set Minimum Order Bottle Quantity to 12 and Minimum Required Product Quantity to 6. Both must be met. See How to set a minimum quantity or minimum spend on a coupon
What happens next
If none of the required products is in the cart, the customer sees "This coupon is not applicable to any of the qualifying products."
If there are some required products but not enough, the customer sees "A minimum of 6 qualifying products is required for this coupon."
With Same as Required Products, only the required products are discounted. Other products stay at their normal price.
With Different Selection, the discount goes on the other products, and only if they're in the cart. If the customer hasn't added them, the coupon is accepted but gives no discount and shows no message. Tell customers what to add.
A Percentage discount on Different Selection products applies to every one of them in the cart. A 100% discount on the Rosé makes every Rosé in the cart free. To give only one free bottle, use Fixed price with Fixed Price Amount 0 and Fixed Price Quantity 1. See What are the coupon discount types?
A Fixed discount on several products comes off the most expensive of them first.
Example: buy 6 Shiraz, get a Rosé free
Required Products in Order: the Shiraz
Minimum Required Product Quantity: 6
Applies To Products: Different Selection, the Rosé
Discount type: Fixed price, Fixed Price Amount 0, Fixed Price Quantity 1
With 5 Shiraz the coupon doesn't work. With 6 Shiraz and a Rosé, the Rosé is free. With 6 Shiraz and 2 Rosé, one Rosé is free.
Troubleshooting
"This coupon is not applicable to any of the qualifying products.": none of the required products is in the cart.
"A minimum of 6 qualifying products is required for this coupon.": the cart doesn't have enough of the required products. Other products don't count.
The coupon is accepted but gives no discount: the Applies To Products products aren't in the cart, or the customer already has a cheaper price on them, such as a 6-bottle price.
The coupon discounts the wrong products: check Applies To Products. Same as Required Products discounts the required products only.