Cranberry juice is a natural diuretic, which means that it elevates your rate of urination. As it also acts as an antioxidant, it is an excellent way through which to cleanse your urinary system. Thus, the logic in recommending cranberry juice is clear. The practicality of it, however, is unclear. While cranberry juice will remove meth from your system (it's often recommended for people who want to go clean and/or are suffering from withdrawal), it's not likely to work quickly enough for you to pass your urine test.
Detox drinks and formulas are pretty common these days, at least in the online market. If you live in a larger, more liberal town then you might be able to find some for sale in health or drug paraphernalia shops. These detox products are usually herbal and contain a combination of vitamins, minerals and natural extracts intended to remove the metabolic wastes that meth leaves in your system. Like with cranberry juice, these detox products are limitedly effective and will not guarantee you a pass on your test.
Your last option is to substitute your urine. Many places that sell drug detox products also sell synthetic urine kits, and you can always ask someone you know to give you a sample of their urine. In both cases, you will have to keep the urine at a temperature of 32 to 37 degrees C until you can offer it as a sample.
There are other options published online, like ingesting baking soda or adding bleach to your urine, but there isn't much information available on these methods, so you might want to avoid them.
Keep in mind that meth passes through your system at a relatively fast rate. In most cases it will be gone in one week, but light or one-time users could find themselves passing a drug test taken as early as two to three days after they last used the drug. Depending on your circumstances, you might not have anything to worry about at all in regard to passing your drug test.