2. To give anal sex
2. Carson got his fudge packed so tight he couldn't shit for three days.
The expression is derived from an assumption that the receptive partner in anal coitus would have his feces, "fudge," compressed and pushed back into the gastrointestinal tract, "packed."
Adam and Steve are quite sore as a result of packing fudge all night.
Leroy does like to pack fudge; some of the other inmates call him "Papa Bear."