Having help write a few and have been fortunate/unfortunate enough to read quite a few; you’re going to need to put at least have an effort in.
The good ones are treated like a thesis, for lack of a better word.
Why should a person/company/business sponsor you? What can you offer them? What do you expect from them in return.
Mine have always included a breakdown of what events I intend on doing, the type of people who go, how many people approx attend etc.
My last one went as far as braking down the cost’s for the sponsor at each event.
I want $XYZpa divided by how many events/ event costings = roughly what the sponsor is paying for each round.
The few really good proposals I’ve read have all been set out all explaining what they want, what they will give in return a bio on the driver and car, his or hers credentials, photo’s of the car etc. One even had a dvd included of the drivers “drift” ability that was taken at a couple of practice days.
Nothing is for nothing, make it professional.