The real question is - "How high is your base level?" If you had no prior THC level in your body prior to smoking on Friday, you will be clean by Monday. If you have a base level built up, it will take longer - Up to six or eight weeks if you are a chronic smoker.
Those detox drinks don't actually detox you, they are a diruetic and vitamins to help you dilute your urine without peeing clear. If you are a chronic smoker, it won't help you.
The best thing to do is nut up and buy a Urinator or Whizzinator to dispense clean urine you buy from a head shop.
Not that I have any experience in this ;-)