How Can Two Unrelated Businesses Cross Promote Each Other?

Internet Marketing expert James Brausch "retired" to South and Central America, but he consulted with some brick and mortar businesses there and he advised two of them - a taco restaurant and a spa - to cross promote each other.

He had the taco restaurant give out, with each purchase, a coupon good for a free 10 minute back massage. He had the spa give out to each paid customer a coupon for a free burrito.

These coupons were not announced before hand, so customers did not know that they would receive them until after purchase. By only giving out coupons to paid customers, he increased the chance that, when the customer used the free coupon, he would be more inclined to purchase from the other business.