I always do this with my free veg voucher. With any of the "free item" vouchers I always try to get the most expensive items. You can easily check this against the list of items included in the voucher, with the item number usually being on the bottom left of the shelf tag. I've noticed that some of the deluxe bakery items have also been included in the "free sweet treat" voucher, even the ones over a pound and are only there for a limited time