We use a product called WineSkin. This is just one brand; there are several out there. They are available online and sometimes at large wine retailers (maybe even small shops). We like these because they seal very tightly.
They are also good for olive oil, honey, jams, lotions -- anything else you don't want sloshing around in the bottom of your suitcase.
I personally have used these and swear by them:
In fact, I just brought home a few bottles of wine from France this week in my Rick Steves' backpack and the bottles were totally unharmed (I've also brought mezcal back from Mexico using the same bags)
-- Mike Beebe
Yes, I've used them successfully too, for several years. I've used them in soft-sided bags. *
I've used a different brand that is essentially the same thing. No issues. However, I would say we didn't have issues prior to the bags. We used to wrap wine bottles in dirty clothes and slide them into a plastic bag, just in case. Wine bottles are actually pretty tough, though no one wants a suitcase with a broken bottle of red wine.
