buy him one
Snickers scenario
If it was really Gates and not a fraud I would buy him one and also buy myself the best thing in the store

Bill Gates makes $127 dollars per second.
I would grab a slushie and 6 movie tickets to Black Widow (if it wasn't during COVID).
Let's say you're walking on the sidewalk near a little store. Bill Gates drives up, opens his window with his credit card out, and says, "hey, would you buy me a Snickers bar? You can get anything for yourself too."
What would you do?