I'm thinking it's clamato juice. I can only imagine that the business meeting or focus group or whatever they use to develop new products went something like this:
"How about tuna juice and orange juice?"
"Okay then, what about caper juice and fruit punch?"
"No way! Disgusting!"
"Pickle juice and grape?"
"Oh my God, that's ridiculous. You're not getting paid for this."
And so on, until they came up with clam juice and tomato which is ingenious, obviously.
I'm going to do the same thing as I did in this post, where I asked you all to top what I claimed was the most awkward word in the English language. So please top my oddest mainstream commercial product by leaving a comment, oh incredibly insightful individuals. I will be giving a shout-out on this blog to whomever I think comes up with something odder than clamato juice.