I was just wondering if anyone knew why alcohol and certain juices can't be bottled?  For example, could say vodka and tomato juice be bottled or does it go bad?  ferment? become moldy?
    thanks

Is there a possibility that there is a reaction over the long haul that changes the taste of the mixture? So even if the product does not spoil it changes. That would be a good reason for not premixing.

Taste change is called maturing and is considered part of the process. That's why most of the herb and fruit vodkas have to be matured for a few months at least. Even some distilled ones are matured - like good plum vodka or black label whisky. It also clarifies some of them.

Some juices can't be clarified this way, or they become disgusting - either in terms of smell, taste or just the way they look. Making good beverage is almost a science on its own

If you spike a juice with enough ethanol it will not any bacterial activity.