Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

Nowadays traders and manufacturers have started to offer too many products, and the people are drowning in stuff. As we see, people have a lot of containers in their houses, or several types of clothing. The companies, as you know, are purely materialistic. They offer prizes to those who buy from them and there is nothing wrong with that, subject to two conditions: 

1 – That the price of the item should be the real price, i.e., the price should not be raised because of the prize. If the price has been raised because of the prize then this is gambling and is not permissible. 

2 – A person should not buy the product because he hopes for the prize. If he buys it only because he hopes to win the prize, and not because he has any need of the product, this is a waste of money. We have heard that some people will buy a carton of milk or yoghurt, which they do not want or need, but they hope to win a prize. So you see them buying these things then throwing them away in the marketplace or outside their homes. This is not permissible because it is a waste of money and the Prophet (peace and blessings of Allaah be upon him) forbade wasting money.