Rinse beans. Wash the red beans thoroughly (Optional: soak 2–4 hours to shorten cooking time, but not required with a pressure cooker).
Pressure cook. Add beans and water into the pressure cooker. Cook on high pressure for 25–30 minutes. Let pressure release naturally for at least 10 minutes, then quick release any remaining pressure.
Sweeten. Open the lid, stir in the red sugar, and simmer (without lid) for 5–10 minutes until sugar dissolves and soup thickens slightly.
Adjust texture. For a smoother soup, mash some beans with a ladle or use a hand blender briefly. For a chunkier version, leave it as is.
Serve. Enjoy hot, or let it cool and refrigerate for a chilled dessert.