I prefer Pepsi too. I muddle through though because I don't drink that much of it. Until recently they didn't carry the caffeine free diet Coke. So I always took some Pepsi brand onboard with me. They don't mind and is allowed within un-defined limits.
One time I walked up to the Lido bar to ask for a cup of ice for my "caffeine free diet pepsi". I was holding the can low because I felt embarrassed to ask for ice for something I didn't buy from them. The Bartender noticed and said it was ok. I ended up sitting at the bar and having a nice conversation with him. He quickly got rid of the pepsi can though before someone else saw it and wanted one.