"Hey. I was hoping to see you around." Here? In general? Nevertheless, Tidus approaches Xehanort with a friendliness, coming near but not too much. Seeing he hasn't got a drink or anything, so he decides to offer first:

"Thirsty? Hungry? Lemme know if you want anything, I can go pick it up."

Let's get this out of the way first - he has a host role to play, in his favourite place of the sports gym. Then, he can actually get personal. --In a friendly sort of way, promise.