We were there last year and got refills in a 2000 mug. Typhoon Lagoon was giving the same mug away in place of the $locker fee refund ($2 or $3 you get back for returning the key).
When we were at Vero in early March they had the refillable mugs. I think it was $7.50. We refilled everything, coffee, iced tea, even just plain club soda at the bar.