This is one of my favorite questions ever. I am a shop manager of a custom install shop and I get asked that question at least 4 or 5 times a week. What you need to understand is that a sponsership is an investment by the sponser in you as the competitor that the sponser hopes will increase their business.
So to answer your question...what recognition do you have to offer to a prospective sponser. Are you Mark Eldridge, the man who has won every concievable prize in car audio. Or, are you Alma Gates, the most recognizable 60+ year old DB-Drag queen in the world. No, probably not... If you ever get the chance to talk to them or anybody else who is sponsered, ask them how much time and money they invested before anybody offered to give them equiptment for free.
They became the most recognizable people in Mobile Electonics before the sponsorships came. Thats WHY the sponserships came. The manufactures that they are affiliated with realized that the attention that their product would get by being in these machines would far outway the costs of giving the equiptment away. Its marketing. If you can devise a way to market youself in such a way, without first proving yourself in the lanes .... CONGRATS!!! Otherwise, hard work and hard earned cash.