I have heard drinking enough water prior to taking a drug test you can pass it does anyone no how true this is?
Not very true.It will be too clear to pass a visual inspection.
The drinks you can get that claim to let you pass work by putting color and other urine markers in large concentrations in your body so when you do drink a gallon of water as they require on your test day your pee comes out the right color and has other things they look for to verify its not a water diluted sample. But that's all it is, a water diluted sample with color to fool them.
Do some google searches on subbing. Subbing is putting synthetic or clean urine in a container that is warmed to 98 degrees and hidden in your pants, and that is given as your sample urine.
In non criminal UAs you go into your own locking bathroom, and that's when you pour the body temperature urine from the concealed container into the collection cup (collection cups have temp strips on them so be sure it's no lower then 92 degrees or they reject it).
Then conceal the container and walk out.
If you can use a friends clean urine that's a sure pass, don't let the urine age more then a few hours at body temp or it starts to smell and they know it's old.
Synthetic urine comes in subbing kits with a container and you mix the powder with warm water just before you use it. It's good for random work UAs if you can get a cup of hot water for your tea to make you want to pee. That gives you time to hopefully mix the powder with hot water, and be sure you carry a small digital thermometer as temp is key.
Tylenol back pain heat pads max out at 100 degrees and are great for wrapping around bottled samples to keep them at the correct temp. A bottle against your body alone will usually not reach 97 degrees.
There is another thread here about this and there are more details.
Hope that helps.