If you use a condom be sure it's non-lubricated & rinsed out. When filled, I'd suggest putting it with a heat pack into a small sock or wrap it up with a piece of light cloth and carry it in your briefs.
Be sure to practice using it in advance with just plain water to make sure you have the temperature range everything just right, and you can carry and use it stealthily, without dropping anything or making any strange squirting noises like when you stop squeezing the bottle and it sucks the air back inside.
Real urine is only good for about 4 hours at room or body temp before it starts to spoil. But you can store it for up to 1 year if it is frozen or 30 days maximum refrigerated. When you warm it up to the proper temp of 94-100f... be sure NOT to use a microwave, it can get too hot. Preferably let it thaw out in the refrigerator overnight first. The best way to warm up a frozen/refrigerated sample is with hot water. Place the sample in its zip-lock bag, condom or glue bottle in a bowl and cover it with hot water. Depending on how hot your water is, you can get a sample from frozen to over 100 degrees in about 5 minutes. Of course that's too hot, but it's easier to cool it off while driving to the test than it is to make it warmer.
Remember that THC metabolites can be detected for up to 4 to 6 weeks after marijuana use. If you have more than a couple weeks notice, increasing your metabolism is probably the most effective way to decrease the time period that drugs can be detected in your system. That means lots of exercise, and high-calorie foods... in that order. While exercising will clean THC metabolites from the system at a faster rate, lowering the detection period, it is important to stop burning those fat cells near test time, because the exercise actually increases the amount of THC metabolites in the urine, so quit exercising about a week before the test... then be lazy and eat big and pack on some fresh, clean fat cells on top of the remaining older ones.
Begin raising your creatinine levels, starting 2 or 3 days before the test. Creatine, which metabolizes into creatinine in 24 to 48 hours, can be raised with red meat and/or Creatine supplement. However, any creatine taken within 24 hours of the test is useless as it will not have sufficient time to metabolize properly.
About 2 to 3 hours before the test, start drinking an 8 ounce glass of water quickly every 15 minutes, so that's about 1 quart or liter each hour. Instead of water you can substitute Gatorade, cranberry, grape or any fruit juice, coffee, iced tea, herbal tea, or soft drinks as they are all good diuretics. The best choice is Gatorade because of its electrolytes and high sodium content. Be sure you have voided dilute urine at least 4 or 5 times before your test. Continue drinking 8 more ounces of water or Gatorade every 15 minutes to replace what you've urinated for a total of about 2-3 quarts in 2-3 hours. If you drink too much water, such as a gallon or more, your sample will be more likely to be rejected as being too diluted. Also drinking excessive amounts of water in the days, or even the night before the test doesn't really help.
At about 3 hours before the test, unless you are aspirin-sensitive, take 4 regular aspirin (not Advil or Tylenol) and also take 4 Rolaids or Tums antacid tablets. Then take 4 more aspirin and 4 more Rolaids again at about 2 hours before the test. Instead of causing a false positive, like ibuprofen/advil is known to do, aspirin actually acts a smoke screen interfering with the EMIT assay, and reduces positive readings for 2 to 12 hours.
At about 1 hour before the test, take a vitamin B2 or B-Complex, with 50 or 100mg of B2. However, if the vitamin is time released, you can either take it earlier with the first 2 glasses of water at about 3 hours before the test, or else you'll need to crush it before taking. Within 30 to 45 minutes of taking your B vitamin, your urine should turn from clear to yellow for the next few voids.
Also be sure to give them your sample from mid-stream, not the beginning or the end of the stream. Start by urinating in the toilet, then quickly stop and go in the cup. Just give the minimum required, 2oz/60cc then stop and switch back to the toilet to finish.
It's very important to do a practice run. You can buy dipstick thc tests at a drug store or pharmacy or order them online to pre-test yourself. They're not as sensitive as a lab test, but they do work quite well so at least you'll know when you've got your method down properly. Everyone is different in regards to metabolism rates, age, weight, body fat % and THC consumption rates. The amounts of liquid and vitamins the time schedule to take them are only general guidelines may be adjusted according to your practice tests to insure the proper dilution rate and color.
There are also many popular home remedies such as fruit pectin (Certo/Sure Gel), goldenseal, niacin and cranberry juice which have been shown to work on many occasions, especially when taken with a couple quarts of water (for dilution) and some vitamin B (for coloring), but they do NOT always work for everyone. Plenty of marijuana smokers have also failed their tests using those remedies, which shows that other factors were involved, such as the amount of water consumed, how much THC was consumed and how long ago, or different metabolism rates. Independent lab tests have concluded that niacin doesn't work at all. Also some labs test directly for goldenseal.
Likewise, using direct additives to the urine sample , such as bleach, ammonia, and Drano or even those expensive 200% money-back guaranteed "detox" additives is risky, not only because they don't always work, but they are also easy to detect since they usually foul up the PH. While they might pass an EMIT dipstick test, they are often either tested for directly, or can be easily detected on a GC/MS test, in which case you'll have to answer for the obvious tampering.