This is a strong article to run-down all the possible discounts and premiums that can be given out with a product offering :

Premiums

a) Gift with purchase

Last Christmas, KitKat chocolates came in Avengers tin containers. That's almost a gift and my son loved it.

b) Purchase with Purchase

If you buy something, you get to buy something else at a discount. Amazon Kindle books now give credits to buy more kindle books and I can't seem to stop buying books because of that.

Discounts

a) "Twofer" 

In Singapore, we call this buy one get one free.

b) Coupons

This is highly irritating. A coupon entitles you to a discounted offering in a future purchase. From what  I know, F&B outlets offering coupons always have the shittiest food.

c) Samples

You get a small sample of detergents or coffee to entice you to make a purchase. Baby milk powder is commonly promoted this way.

d) Contest / Sweepstake

A contest requires some skill...