No technology, no treats, no tv.
Early to bed.
I would have come down on this the first time I heard it like a tonne of bricks.
This behaviour is the result of children not being corrected the very first time this happened.
They need an extended period of zero tolerance and firm consequences.
I have come across children like yours, that had nice, but ineffectual parents.
I kept my children so far away from them.
I didn't want my children around that type of behaviour, and the parents who would accept being spoken to rudely.
Unchecked it gets worse and they are actively avoided by nice families.
By the teenage years they are totally out of control.
Take their behaviour so seriously because what it morphs into unchecked, is a disaster.
Apologies if that sounds harsh.
But believe me when they start speaking to you like that in front of other parents, word will get around.
Your children will pay a heavy price for not being taken in hand.
Make their lives a lot less fun and comfortable.
Not treats, no technology whatsoever, no outings, early to bed.
Zero tolerance.
Children are very smart.
They will very quickly catch on that their bad behaviour will have consequences.
Good luck.