ORIGINAL: Sport_Pilot
if its been sitting around with a hole in the cap the menthanol is probably saturated with water
Only if stored under its flast point of 51 degrees F. The fuel will not asorb water when it is evaporating. It will be at a very slight positive pressure with vapors slowly pourning out the hole. Besides your engine will tolerate a lot of water, and you will be adding fresh methanol to the mix.
I could be wrong, but I believe fluctuations in temperature, such as the difference between day and night during the summer, can result in high humidity air being sucked into the bottle. When the water condenses on the side of the bottle, it's going to end up in the fuel.