While receiving oral sex, when a guy is about to come, he shoots the jizz in his partner's eye, and then punches her eye so that it swells up and shuts with the blood and nut trapped inside. The swollen eye with the mixture inside is similar to a jelly donut.
Note: it is the actual swelling/closing of the eye that makes this feat a "jelly donut."
"Dude, last night I gave Carla a jelly donut. She was none too pleased."
Guy: "Wow, waht happened to your eye? Are you okay?
Girl: Yeah, I'm fine. Clarence gave me a jelly donut last night.
Guy: Sweet.
When you're having sex and just as you're about to cum you punch her in the face and nose repeatedly until there is plenty of blood, THEN you cum on her face. This resembles a jelly donut.
"Me and Martha were having sex and I punched her in the face heaps until she was bleeding and crying for me to stop, then I pulled out and came all over her bloody face, it was great, like most jelly donuts are"