haha no you should fill the cup with hash oil and be like yeah my piss is about 90% thc on a serious note just pick up one of those detox things from a headshop and drink shitload of water
piss all over the cup and on the outside of the cup and give it to them and then leave. that way they won't wanna touch your cup to test it cause there's pee everywhere
lol wow. and yeah OP, if you water it down that much, the levels of everything else in your pee will be fucked up. They'll just make you take it again.