Knock knock. This is the police. We have a search warrant. Please let us in whenever you get done flushing all the heroin down the toilet. Thanks.
I could have typed your response for you. Yup that's it. Flushing all the evidence down the toilet. That may have worked as justification in the 1970's but not today. Not a chance. Now think long and hard for a real reason.
Better yet let me save you the time. There aren't any.
Before no knock raids got invented they just turned off the plumbing. No flushing then.