I don't suppose you have ever drank in excess?Essentially there is a hormone in our body that controls the release of water in our body (ADH). Alcohol is known as a diuretic, essentially it will cause our bodies to release existing water in our bodies which will pass into our urine. Leaving your urine colorless due to how "hydrated" it is (Your body isn't, but your urine is diluted by all of this).