I've never heard of it. I'd be reluctant to try it unless I had some extra seeds I didn't mind losing. It may work, may have no effect. It seems that for ever recommendation to soak the seeds in something, there are an equal number of warnings against doing so. Patience seems to be the only dependable factor in getting them to sprout!

Well, I tried it. I found a website that said 5% ethanol for 24 hours, so that's what I did. I'm sick of babying these stubborn seeds! Don't they know their purpose in life is to sprout? Sprout dang you! I've already tried the cold period (twice), the orange juice, the hot humid greenhouse, the waiting months, and some very stern looks-with-a-finger-waggin', so I had nothing left to lose. I'll let you know if anything pops up in the next month.

I found this on the easywildflowers.com website:
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Passiflora incarnata Passion Flower seeds are slow to germinate, they contain a natural chemical that slows their germination. This chemical is slowly removed by contact will cool damp soil. It is possible to germinate them faster by giving them a pretreatment. I received the following emails from two of my customers describing the successful pretreatment they used.

email from Sandy - "Just a short e-mail to let you know that your Passiflora incarnata passion flower seed, sown Feb 22, is germinating (March 1). Was given a 24 hour soak in 5% ethanol cider (changed twice) on gentle bottom heat. They are now peaking through the medium (20 sown 3 are up) and are under grow lights. Passiflora have a germination inhibitor that is more soluble in alcohol (mimics the natural fermentation of fallen fruit) than water. This info is from a master gardener I spoke to months ago. In a couple of months the little passifloras should be in one gallon containers judging from their vigor"

email from Kristl - "I had never grown Passiflora incarnata before and all the info out there seemed to indicate a warm-cold-warm pattern. Instead I tried treating it with GA-3 (overnight soak). This was about 2 weeks ago. As of yesterday about 80% had germinated." The GA3 Kristl refers to is Gibberellic Acid, a chemical often used to improve germination of seeds that are normally slow/difficult to germinate.
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I usually soak them in orange juice, which is supposed to mimic the acidity of the fruit. Maybe you could add a little ethanol cider (not sure what that is) to some orange juice?

Ethanol cider would be fermented apple juice.

I have grown many passies from seed and I find the main thing to assure fast germination is to have very fresh seed. The older the seed the harder the germination. When I plant my own seed I do not dry them. I just remove them from the fruit and plant immediately. Germination is usually within a week or so if kept warm.
Patsy

I've had some take 2 years to germinate.. Cource by then the tag is all bleached & I haven't a clue what they are. Some have even volunteered in the yard or other pots where I threw the "that didn't work" potting mix.

All I can do now is wait for a flower.. Sigh.

When I grow passies from seed, I mix the seeds in a pot of dirt and cover it with cling wrap and usually in 2 weeks there are sprouts. Scarring the seed for faster germination is always a possiblity (but if they are kept warm, I don't think it matters). You could also look in to giberellic acid - that overwrites germination inhibitors. I added some (and too much) to a full grown passion vine and it resulted in 6 months of minature growth (TINY TINY TINY flowers and leaves - could hardly tell what they were), but now that it is getting full sun, it has resumed normal growth (and has 8 buds on it right now =)).