I like that this has become a sort of election tradition now lol.
If I can propose a slight tweak, if you know he's heading your way might I suggest buying the milkshake about a week beforehand to allow it to reach it's full potential? Let it level up, so to speak.
People throwing mysterious liquids over other people is a problem, even if it can be comical. Imagine if it had been one of those nutters throwing bathroom cleaner.
It's only a matter of time before you'll get 20 years for a milkshaking. I remember when that weevil Ngo got milkshaked, there was endless handwringing and gnashing of teeth over it: "What if someone were to put ready-mix concrete in a milkshake cup? Anthrax? An HIV-riddled bloodshake??" And of course, none of those escalations happened, but it clearly discomfited the fringe political enthusiasts.
It's important to have non-lethal physical means of expressing derision. It used to be banana-cream pies, but it seems that those days are long gone. "They came for the milkshakers, and I did nothing..."