Here we are going to collect and share information about how to fund your event or open source project. If you have anything to contribute - pls. do.
A good way to approach sponsors is to make contact with a sponsorship brochure and continue the discussion with a follow up mail. You can download adaptable sponsorship brochures for OSCEdays events here.
You can ask ppl. for donations. Paypal offers an easy way to do it - it is good for one time donations. If you have a longer project running Patreon is a very popular website. It allows people to support you on a regular basis. A similar website is Flattr.
You can sell tickets. There are also good services that help you with that. In Germany Eventbrite is very popular in Germany. There will be probably similar websites popular in your region.
You can use your events to sell products. At the event. Or in an online shop and use your event to point ppl. to it.