Here is a lame but kewl trick.
You need a kitchen sink with one of those dish sprayer nozzles that are attached to a hose.
Prior to committing the joke, tape the lever so that it is in the "on" position and replace it so that the sprayer is facing forward.
Wake up early in the morning and ask your victim to make you some coffee. Usually, people put the tap on full blast to let the water run before catching water in the coffee pot.
Obviously, with the tap open, water sprays full blast at your victim.
Depending on how early it is, the victim may turn the tap off only to turn it on again before realizing where the water is coming from.
Potentially sexy April Fool's joke for female victims with white T-shirts.