Put em into their mouth.

I'd ask what they're for?

“Thanks! Same time next week?”

My first thought is to give it away, what I know for sure is that I would light that money on fire before I kept/spent it myself, no way I hang onto it

I’d be wondering who they had mistaken me for, and let them know that and return the money.

Hm, probably a mistaken person and they will come back and demand the money back. Nevertheless I could say:" Thank you darling, my pleasure!" .. and vanish in the tiny alley ways we have here.

"I think you have me confused with someone else." and maybe "I don't know you."

I'd hate to take their $1000 that's meant for someone else, unless they're rich af, but I wouldn't know that.