Put the cornstarch into a small bowl and add 1 Tablespoon of juice from the pineapple. Stir to combine and make a cornstarch slurry. The mixture should be smooth. You can add more pineapple juice if needed.
Dump the remaining pineapple with juice into the Cold & Hot Blender, add sugar, rice vinegar, and red pepper flakes. Add the cornstarch slurry.
Put the lid on the blender and select cook on high. Allow to cook for 2 minutes, then hit pulse twice. Continue cooking on high until it comes to a boil, this takes about 2-3 minutes.
Cancel the cook function and select smoothie function. Serve & Enjoy!