I just got here and went to buy the mug on Saturday. I had seen some people with a brown one and I couldn't find that color at Ulu cafe so I asked the cashier if maybe there was others colors in other locations. She said "I don't think so, they are probably using an old mug they brought". She didn't say it in a sarcastic or nasty way, just a matter of fact way.
As well, once I got the mug and started filling up, I've already seen people filling up with their own water bottles, a poweraide bottle and a Starbucks coffee cup.
Seems to me that Disney already accounts for some loss in revenue in this situation.
It is not environmentaly friendly to have these mugs be purchased every visit, so I plan on re-using my mug on future trips to Aulani.
We all have our own personal level of what we'll do and what we won't. Berating someone for having a higher or lower level than you is pointless.
Drink on everyone