Stir together the apricot jam, rice vinegar, soy sauce, powdered ginger, and garlic. Use a fork to squish the plum into the sauce, if using. Mix well, taste, and adjust with rice vinegar (and sugar, if needed) to balance the sweet-tart contrast. Enjoy!
Notes
The sauce will keep, in a clean, airtight container in the fridge for up to 1 month.