It sounds to me he doesn't understand what money means. My nephew was like that - for him it was shiny coins and buying things was a great game. But they don't understand it's a finite resource and it's not a toy.

If he's giving money away, he may think it's logical to take money off someone when he doesn't have any. I wonder if you need to stop giving him money until he understands the process more. Or maybe need to sit down and explain how money works. I'm not sure if they understand at that age. Maybe talk to his teacher about when kids learn about money or how other kids that age handle money.

I dont think you should give him something just because he asks for it or sulk if he doesn't get it. That doesnt teach him anything. Does he do this with toys etc?

it may be an opporunity to teach him about basic budgets. $x buys 'n' things. Once it runs out, it's gone. I wonder if you can make a game of it if you give him $1 a day and then see when he can handle $5 a week and not spend it all at once. there's a great board game called Cash Flow for Kids that teaches kids about money, but I think it's from age 6 and also, it's really expensive.

Right now, he's learning about consequences of actions. it will take time, but he'll get there.