Okay just for clarification:
It is $5 to buy a wristband and you absolutely do not need to be a pass holder to get it. If an employee asks for your pass they are simply scanning it for fun perks and half the time do not even explain why they are scanning your pass.
At the beginning of the season there were two option: Free refills in a souvenir cup or unlimited 20 oz. drinks. Yes, this later option was and is abused. The guest is allowed to go up to any stand and get one free drink. Then they are free to hand that drink to a family member or friend and go to another stand or even just get back in line. The system was flawed but there is not much way around it.
I have noticed a dwindling number of the 20 oz wristbands. They are given to large groups and I sometimes still see them. I'm not sure if you can still purchase them maybe at the front of the park or if they are just reserved for the fun perks rewards now- but you cannot find them at the stands anymore.
All that the stands have are now the refill wristbands. The wristbands DO specify what day and which option you have. Regarding icees: You cannot use your wristband to refill icees at mix-it-up. However, subway is allowing free refills on icees with the wristband. Now wether they are supposed to be allowing it: i'm not sure. But they are.
Hope that helped clear things up
EDIT: Also I have heard that it is possible that the $5 unlimited drink wristbands were only available for purchase pre-season, before the park opened full time for the summer. Also this information is 100% accurate, not just an assumption.