I think the OP meant those refillable bottles they sell in the park at AK.
Last time we were there (December) they cost about $7 or $8 and then refills were a little less than $1. You could refill them in the CS & carts of the park with soda, ice tea, lemonade... you can't use them in other parks.
I was going to buy one until I saw them. They're HUGE and would be a pain to carry around all day.