So, I did once, so I thought you could... but I’ve tried twice since then and been told no. One bartender offered that I was probably only allowed to do it on an occasion where they were out of the mugs.
It’s too bad, because I like the drink! I paid like $14-something for it sans mug, and it would be one of my Oga’s go-tos if it was an option.
I don’t think I’ve been to Oga’s since early November, though, so it’d be worth asking again.