If I wanted my whiskey mixed with cola, could I say "I would like my whiskey watered down with coke."?
No. Just say
'Whiskey and Coke, please.'
Rover
Only water can be used to "water down" something. Still, if someone wanted whiskey and water, he would order "whiskey and water," not ask for it to be watered down.
The phrase "watered down" in the context of bartending implies that some dishonesty is going on. That the liquor itself has been watered down prior to being served.
Exactly.
Not the quality, but the strength.