Drink as much water as you can right up until the test. This will dillute your piss and make it more difficult for a strip test to catch you. If it goes to a lab your done. Take half of a multi vitamin the night before so your piss is still a nice yellow color and not clear from all the water. Don't "save" your first piss of the day, it's way more potent. Don't let the first half if the stream hit the cup, only collect the last half...and good luck.
Two days isn't really enough time, get someone sympathetic to your cause to donate $$$ for a flush.