True, it must be cold to carbonate, but then once sealed in an air tight container, it can get warm. It’s stored warm in stores all the time, just drink it fast after opening it off the shelf.
NOW…technically we were talking about Cola…Dr. Pepper is very different.
Many people enjoy mulling Dr. Pepper (remember it has those secret spices–so technically heat it and it’s pre mulled). What many people do is heat Dr Pepper, like Tea or Coffee and then add a lemon slice. It is, surprisingly good.