Slice the Spam into 8 even slices.

In a bowl, mix 3 tablespoons of soy sauce, 2 tablespoons of sugar, and 1 tablespoon of rice vinegar to make the marinade.

Marinate the Spam slices in the sauce for about 15-30 minutes.

In a skillet, fry the marinated Spam slices until they are crispy and golden brown on both sides.

Take a musubi mold or a small rectangular mold (or improvise with clean, empty Spam can) and place it on a cutting board. Place a piece of nori on the bottom of the mold.

Fill the mold with a layer of cooked sushi rice, about half an inch thick, and press it down firmly.

Place a slice of fried Spam on top of the rice.

Add another layer of rice on top of the Spam, pressing it down firmly.

Press the top of the mold down to compress the layers.

Remove the mold carefully, then wrap a strip of nori around the musubi, sealing it like a present.

Repeat the process for the remaining Spam and rice.

Slice the musubi into bite-sized pieces and serve.