Cut your cinnamon rolls or biscuits into 4 pcs. per roll or so. Put into a bowl.
Add your white sugar and cinnamon into a large baggie, mix together, add your cut rolls and gently toss so they are coated.
Spray the inside of your 6 c. bundt pan with non stick spray. Put 1/2 of coated cinnamon roll / biscuits pieces into pan. Pour 1/2 brown sugar/butter over that. Then layer remaining rolls with butter mixture on very top. Sprinkle in nuts here and there if you want to add those.
Pour 1.5 c. water into the inside of your pressure cooker and lower down a trivet. Then lower filled bundt pan loosely covered with a piece of foil on to your trivet.
Close the lid and steam valve and set to manual, pressure, high, for 20 minutes.
Do a natural release for 10 minutes. Then release rest of steam.
Carefully lift out, and allow to cool almost completely on a cooling rack before flipping over if you want it to stay in tact. If you want it warm flip over immediately, it just may not stay in tact as a pretty looking bundt (but really who cares).
Can pour icing that came in cinnamon roll tube on top of that too and enjoy.