create a loyalty reward scheme and communicate it on/in-pack, in-store, on brand website or CRM program
various reward schemes available: get 5th free, collect points with every $10 purchase, increasing discounts (-1$ on purchase 1 >> -2$ on purchase 2 >> …), etc.
various compensation mechanics: consumer cashback, coupons, gift vouchers, free product or goodies,…
use as stand-alone or fully integrated within CRM program