Sounds like you are already fat adapted, so I wouldn’t expect to see excess ketones in your urine, since your body can use ketones for energy efficiently. People that aren’t fully fat adapted will produce excess ketones that will show up on the pee strips. Being keto long term, I’ll never show ketones on test strips.
It sounds like you have not completely burned off all of your sugar stores. Your liver can store up to a pound and a half of sugar as glucose. And if you have excess sugar in your blood in addition to that and insulin resistance it may take you a while to burn off your sugar stores. Your body will only start producing ketones as a byproduct of burning your fat stores. Your body will not start to burn fat stores until all of its glucose and glycogen stores are depleted.
That being said, urine test strips are the most inaccurate way of trying to test ketones. I would suggest trying a ketone breath monitor. The Biosense one is a little expensive but it’s pretty good.
Honestly this makes no sense. You are not fat adapted if you don’t eat a ketogenic diet all the time. You are yanking yourself out of ketosis, which stops the fat adaptation process (which takes weeks or longer to achieve, while eating a fully ketogenic diet). And why are you so concerned with ketosis when you are just going to yank yourself out of ketosis again? I really don’t think you understand keto or fasting tbh.