There are many different ways and remedies to pass a urine drug test. It can be supervised or unsupervised. Supervised means someone will stand next to you and watching your dick while you are urinating to prevent using fake or someone else urine. So in this case synthetic urine wont work,unless you have a fake penis, something like the whizzinator.
I always suggest for everyone to use detox drinks for THC test because these are always give good result and doesn't require a big investment. The best marijuana cleansing drink is MegaClean and Rescuse Cleanse. Mega Clean is the best detox drink for drug test and that's why its to most expensive. Well, not really expensive, because it costs 69$ and it saves your job/freedom. Rescue cleanse is slightly cheaper, but I am not sure about the current price, because i always buy MegaClean.
You can buy some really low quality detox drinks in walmart and on amazon. Please do yourself a favor and stay away from crap like Qcarbo,Stinger or Vale detox, these are all crap,same as certo, not recommended. If you wanna gamble then goahed, but if you wanna make sure you pass your urine drug test, then Mega Clean is the way to go. Where easy to use, just drink the full bottle one hour before the test, then refill the bottle with water 2-3x and drink it, you want to urinate as many times as possible before the test.
Its recommended to stop using weed, before the urine drug test, do some exercise if you can, try to sweat as much as possible(because THC is stored in your fat cells) and eat lots of fruits, veggies and other fiber rich foods.
If you bought the right cleansing drink and follow these advices I can guarantee that you will pass your drug test with flying colors.