"Hi, could I have a grande vanilla iced-coffee?"
"And your name?"
"Is that Zach with an ch or Zack with a ck?"
"You know, I've even seen it done with just a c. But really, isn't this what we have regular expressions for?"
The barista hands over the pen and cup, whereupon the customer writes:
"There. Now you can't possibly be wrong!"
I can just imagine someone trying to pronounce this :P
"Vanilla Iced for Zackkgcckhk?" (Complete with rising inflection on the question mark)
Also, I prefer the randomized algorithm: Just write "Zach" on the cup. The sound of the name is all that's required to get the drinker's attention when it's ready, and because so many different-sounding names exist in the English language, W.H.P. there won't be any issues distinguishing whose drink it is.