A letter asking for corporate sponsorship should provide detailed information on the reason for the sponsorship request, the program being sponsored and the benefits of the corporate sponsorship. The main objective of the letter is to convince potential donors to contribute funds toward a certain cause.
For a letter only requesting a small donation, a brief overview is generally enough to suffice. For example, a small amount of information on the organization requesting the money and what the money goes toward is plenty. Noting how much of the donation goes to the charity increases the odds of finding sponsorship.
For requests of larger amounts of money, maybe to fund a charity or start a business, include more information in the letter. The same basic overview required for smaller amounts should be included, but also note other important aspects, such as how much income potential is expected, the return on investment or the business proposal.
No matter the type of sponsorship, address the letter to a specific business or person, and use a formal tone. A letter looks more professional when free from spelling and grammatical errors. The letter should include contact information for responding or sending the donation, as well as information regarding the donation being tax deductible.