Add water to a small pot along with soy sauce and sugar. Bring it to a boil, and gently boil over medium heat, until the sugar is dissolved. Turn the heat off, and pour in vinegar. Adjust to taste if necessary.
Pour the hot brine over the vegetables. If the vegetables are tightly packed in the jar, you don't need to weigh it down. However, make sure all the vegetables are submerged in the brine.
Close tightly with a lid, and leave it out at room temperature. Then refrigerate.
Optional: To keep the pickles longer, you can pour out the brine into a pot and boil it for a few minutes.