There are many benefits to the humble hot dog: they're easy to prepare, simple to eat, and straightforward to sell, so they offer a useful way of raising some funds. Find a local retailer willing to let you set up a hot dog stand outside their entrance and you're all set — be sure to have everything ready to go before lunchtime, as that way you can catch hungry shoppers as they leave the store on their break.
Pick the right grocery store and you'll find you can purchase everything you need without having to go anyway else. Alternatively you could buy in bulk at a larger club store.
As well as your hot dogs and buns, don't forget the ketchup, relish, mustard and other potential toppings that you might want to turn to, as well as napkins. If you want to, you can sell chips and sodas as well, though you'll need the means to keep your drinks cool for long periods of time.
The hot dog stand idea can also work down at the local park or at community events such as the next 10K run. The best part is that your hot dogs and extras won't cost you much, so you can sell them pretty cheaply and still make a profit. Visitors to your stall can have a quick, satisfying meal without spending too much while you are making money for your group.
do i need a license of some kind? Just a one day event for a 501c3?