My youngest went through TERRIBLE twos. I avoided shopping with him as much as possible.
Once I took him to the grocery store and he wanted to buy some candy and I did not meet his demand. He arched his back and thew himself on the floor, crying. I just kept walking with the other kid and stopped at an isle around the corner. All these shoppers gathered around him looking down. He had his eyes closed. When he opened his eyes, he stopped crying and screeched for me. I said “We are over here.”
He did not pull that trick again. He was mortified. Better he embarrass himself than take me and his brother down with him.
Quite wise, yet that could put you on a watch list in some places with the increasing laws against leaving any child unattended: http://www.freerangekids.com/laws/