You can use someone else's week old urine for a drugs test, but ultimately, you'll be caught out for trying to cheat the test. Here's why...
Before even mentioning the fact that you're likely to be caught during the test itself, the temperature of urine has to be considered. If you're taking part in a drugs test at a test centre, your urine sample will be tested quite quickly.
What this means is that the machine will be able to check whether the urine has been passed recently by it's temperature. Someone else's week old urine will raise alarm bells instantly due to the fact that it's a lot colder than it should be.
The likelihood of being caught red handed
Another important thing to consider is that you'll likely be in a room with an observer when you go to provide your urine sample. It's their job to make sure you don't try to switch urine samples or do anything else to try to trick the test.
If you're in the room trying to pour someone else's week old urine into your sample cup, you're definitely going to be caught.
What are the options?
It's quite straightforward, and not the answer that a lot of people want to hear, but the best way to pass a drugs test is to not take the drugs in the first place. The test itself accounts for people trying to cheat, and will look for any suspicious signs. Likewise, the staff at the test centre will be on the look out for anyone trying to cheat on the test.