Prior to any claims about an affair, Tiger Woods was one of the most decorated athletes in the world. He has made millions in endorsements from many different companies. He even has his own line of Gatorade, the most popular sports drink in the world. Tiger endorses Gatorade's line called "Tiger." This product says it is made for athletes that word hard and need to focus. Here is a picture of one of the ads.
Since Tiger is among the world's best and most successful athletes gatorade jumped at the chance to use him to endorse their product and even make a product with his face on it. This makes sense because he has proven that he is an example of a hard working athlete. This gives him perfect credentials to endorse their products that are targeted towards people like Tiger. This was an excellent choice for gatorade. However, the product itself did not do as well as Gatorade had hoped it would. But, Tiger Woods benefited greatly from this endorsement. That is until his recent scandal when Gatorade dropped him from the campaign. So, all in all this was not a successful endorsement by either parties.
This article from 2007 discusses some of the details of the deal with Gatorade. Tiger benefited greatly in terms of money from this deal. This article says that he was also considering Vitamin Water at the time the deal was made. Gatorade was just another brand on Tiger's long list of sponsors.