I usually press play on the pre-recorded speech and give them the option of walking out or sack of potatoes.

“ I know you’re frustrated xyz happened, it was disappointing this happened when you wanted that. It’s ok to be upset, but right now we’re in a public space, and we need to respect that other people who aren’t having a hard time are trying to enjoy themselves so we’re going to go to the car and chill until our brain cools down, ok?”

Tantrum proceeds

“You have two choices, we walk out of here together, or I can carry you out like a sack of potatoes, what’s it gonna to be?”

Sometimes she gets excited to be a sack of potatoes and the tantrum is cut short, sometimes I thank the heavens we look alike because I’d rather not have the police called for a kidnapping attempt.