10 percent will be donated? That is outrageous. If you are serious about doing a fundraiser, you should be donating at least 75 percent to the chartiy or it is not a 'fundraiser' is it just a money maker for YOU. Good luck convincing anyone to give you a dime for anything - why would anyone donate 90 percent to you when they could donate 100 percent directly to the charities.
Okay - read your comments. I can make two suggestions:
1 - If you are fundraising for a racing team, to be honest, you should say that - you should remove the 10 percent to charity as it is confusing and misleading. The companies or individuals likely to sponsor you won't be impressed, and it initially seems very misleading.
What you can do to fundraise at absolutely no cost is to approach local companies and ask them for sponsorship. You will need to determine the benefits of sponsorship - logos on uniforms, on the racing equipment, listings in journals, or whatever you decide, and then you can approach the companies and ask them to sponsor your team. If you target stores or companies that are likely to be somehow involved in the type of racing that you do, you will have a better chance of success.
Alternately, if you want to host a dinner or lunch (or a fundraising barbeque!) you can ask local stores to donate items for the fundraiser - perhaps a local bakery would donate buns/bread, and another store donate the sodas/beer. You will have to think of a way to give them appropriate recognition for their donation (again, logos, signage, or something that makes it worth their while).