This isn't a bad prank but i'll tell you anyways, my parents were partying downstairs one day, they were both drunk, listening to loud music. So I took an empty beer bottle, filled it up put it in the fridge, when my dad went to get a beer he got that one. It was so funny, he opens it he's like "wtf" and starts to drink it,
My dad: Norma(my mum) this tastes like water
My mum: no it doesn't
my dad: no seriously, try some, it fuickin tastes like water.
my mom: I'm not gonna fuckin drink that.
Then I just bursted out laffing....
That's the only prank fresh in my memor.