there you are (informal English, there you go)
I think the phrase should be used when giving something to someone but after a request for the special item, like in a shop.
a customer asked me for a new pair of shoes and I've found it on one of the shelves. giving the shoes to the customer I say there you are.
in other situations we usually say here you are
giving to someone a glass of water, a cigarette, a handy tool or something