Sour doesn't really work well in vape, but I have had some success by using capella powerful sour, but there's a trick to it. You have to open the powerful sour and let it air breathe for 14 days. Then it becomes crazy sour and works well in juice.
Hope this helps someone, I discovered it by accident.
When I was on a sour kick, I used...Lorann's tart n sour I think it's called? It worked well enough...for a short time before flavors got muted. Also, this was back in the early wild West days of DIY, when I wasn't super concerned about what sorts of wacky chemicals my lungs were taking in, so...meh. nowadays , I'd look into lemon flavors. Not sure which, though
I think Flavorah's sour apple is pretty good. The recipe called Awesome Apple here is super tasty. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.flavorah.com/wp-content/uploads/FLV-Vape-Recipe-Book-1.pdf&ved=2ahUKEwi05_rLr-TlAhUGHcAKHfdKATEQFjAKegQIBhAL&usg=AOvVaw13cszMw50RVdwsU8cDPgR7
Sadly, you're not going to find anything that is truly sour. Maybe more tart than anything, but I've tried every sour additive on the market solo, combinations of those, and made my own citric and malic acid dilutions to try and replicate any sensation of sour, no luck. Most of the vaping experience is actually being processed by your nose rather than your tongue. An interesting experiment to try is vape something you know the flavor of like the back of your hand, then vape it while plugging your nose, you're only going to get vague sweetness if anything. Pretty interesting right? The only way to get pucker sour from your juices would be if they actually spit back and make contact with your tongue, which I doubt you'd be into.
That being said, some things that can give the illusion of a sour quality could be more tart or rind-y fruits like VT boysenberry or some sort of melon by FLV, those seem to have more rind notes than any. Or give WF SC sour ball candy a shot.
As others have noted, sour is extremely hard to do with vaping. You can get tartness by adding in some lemon flavor -- I have used small concentrations of INW Lemon Concentrate (.5%) and Lemon Mix (.25%) together with any fruit flavor which brings out a different side to those flavors and balances them well. That is the best I have been able to do.
INW Lemon Mix
- tart lemon zest flavor.
FW ecaffeine
- caffeine as a flavoring agent is bitter. It may also be of use to you for placebo effect. Oh wait, I might've just ruined that. Ignore that last bit.
Actual sour... Not happening.
Camp Tiger Claw is pretty decent, I adjusted it slightly for my taste, but it is a solid sour candy apple flavor if that is something you are interested in?
I did 1.5% on sour apple and 8% on green apple hard candy. The original recipe is a bit heavier with the %. You can find it on ATF. It is my all day vape currently.
Edit: forgot the “Camp” in Camp Tiger Claw”
Well, a sour vape is kind of an illusion or trick on perception, since the flavor is pretty much perceived through the olfactory organ, rather than the tongue. Smells can have many qualities, but nothing comes close to the sourness you'd taste on your mouth.
Having said that, some fruity, fresh flavors can achieve this effect.
There are many flavors you'd expect to be 'sour', but they turn out more bitter or sweet and... Rind-y? Yes, i'm talking about most of the citrus flavors I've tasted. I've had many Lemon flavors, from TFA, CAP, FA, and INW. while they could capture the zest side of the fruit more or less adequately, they do not feel sour. The only notable exception has been INW shisha orange. That is a candy-like orange that smells sour to me. Oh! If artificial lemonade is your thing, then LA lemonade may be just for you. Also, CAP Sweet tangerine smells fresh enough, but it's still on the sweet-sour end and it needs help to be a full flavor.
Berries... The one that comes to mind as 'sour' is INW raspberry. All the other berries that come to mind are on the sweet end. I have not had success with making, say,a sour strawberry, but I would LOVE to have that.
Melons. I hate melons. Or at least I think I hate them. The point is, I haven't tried so I can't help.
Cherries. Again... They tend to be sweet. TFA black cherry is too sweet. TFA maraschino cherry, just not worth it as it will have a faint cat piss quality. If anything, FW Cherry Crush. It's still sweet but it's workable. Maybe, adding it to a lemonade base you'd be able to create this sour illusion. I have not mixed that in a while, but FW Cherry Crush with FA Lime Tahiti have worked for me in the past to create Cherry limeade.
How to forget.. Pineapple! TFA Pineapple does smell fresh, and may work.
The tongue can sense salty, sweet, sour, bitter, and umami. Those have nothing to do with the olfactory system. The olfactory organ allows you to determine actual flavor like garlic, rosemary, strawberry, etc.
Edit: vaping does not only affect your olfactory receptors. It also involves the tongue.
Cherries - here goes. You want GL Cherry, TFA Cherry Extract, and INW Cherries. In addition, TFA cherry blossom and FA Marzipan are also useful in the cherry game.. (Marzipan will add sweetness to a mix with a hint of cherry. Cherry Blossom is basically a floral cherry flavor, which can turn a mix towards a candy, strangely enough.)