When charity works
The Wondergirl 5k, produced by Girls on the Run, attracted about 4,000 participants on a hot morning in Chicago IL. It's a successful event because running is central to its mission - it doesn't just use a race to try to raise money for a cause.
Companies can become sponsors or merely contributors (those are not the same). Some businesses may support the cause, or simply want to be identified with it, and might be less demanding about marketing entitlements.
The race was non-competitive - there were no official results. A clock was visible at the finish line for those who wished to time themselves. The event was less a race and more a rally to culminate a season of training.
When conceiving fund-raising ideas, it helps for the venue to be relevant to the cause.