Nothing brings in money faster than strippers and booze, unfortunately. The next best would be pizzas and/or hoagie/submarine sandwiches, preordered and delivered on a particular night/weekend. If you can work out a wholesale deal with a local business, and deliver them yourselves, it can pay. Knowing the project is for a good cause might make people tip well too.
The bar-b-que with games, like toss a softball into a bushel basket tipped at 45 degrees, or toss a coin and land on an upside down glass, where you win a cheap prize plus bragging rights, can be fun and productive.
Selling protection, while wearing a fedora and bulging coat, works too.
