You can purchase length so stay mugs at the resorts. Sorry, I can't remember how much it costs.The parks and the hotels do not share the same refillable cups. If you want one in the park and at the hotel, you would need to buy them separately.
In the parks you can reactivate a cup for around $9 per day or you can just pay for refils at $1.50 each.
I don't know how it works at the hotels.
Reminder that the popcorn buckets don't fit in the small lockers outside of the rides (they will fit in the bigger ones you now have to pay for). So something to consider about lugging the popcorn bucket around all day with you.