I love a sweet flavored coffee vape and to drink. Lately I'm always with a cuppa fancy (homemade) joe in one hand and (DIY) coffee vape in the other. Yes, typing is a challenge, lol. I've tried many flavors and here are the ones I've found best so far.
Nature's Flavors Organic Coffee: This is my #1 for mixes at the moment, 10 stars, 2 thumbs up, and all that. Alone it reminds me of a coffee flavored hard candy. No bitterness, smooth, and it totally stands up to all the additions I like. If that sounds good you must try my Fabulous Carmel Mocha: 1 part of this, 1 part caramel, 1 part chocolate. I use FlavorWest's Double Dutch choc and Caramel Candy, and mix 5% each for 15% total flavor. Other choc and caramel flavors work fine, those are just my current favorites. No steep required, and if you're a StarBucks-type-coffee fan, you'll vape yourself silly.
Capella's Espresso: true espresso taste with LOTS of sweet, no cream. It's a good base. Mix with at least an equal amount of cream flavor for a good cappuccino base. Then add Irish cream, vanilla, cinnamon... whatever flavors grab you. The espresso taste is very bold IMO, so if you want COFFEE with flavorings, this is a good base to use. If you prefer coffee with FLAVORINGS, use the others.
Capella's Cappuccino: Sweet, creamy, smooth, very full mouth feel to me. I mix at a bit less than 15% and add a tad of Capella's Gingerbread (total flavor about 15%) to make a super Gingerbread Cappuccino.
Capella's Cappuccino + Capella's Espresso, at 5% each is very good! That gives the sweet, the cream, and a less-strong espressing, still leaving room for 5% more of whatever flavors you add. Vanilla and sweet cinnamon?
Nature's Flavors Organic Kona Cream: Very smooth, very creamy, not cloying, a somewhat smokey finish, and Very Voluminous Vape. Really, it makes thunderclouds

The Kona flavor is right on, and I don't adorn or alter this one at all. I mix at 15% flavor, 65/35 pg/vg. With 50/50 pg/vg mix you won't be able to see across the room. Note this is Kona CREAM flavor, not their plain Kona, which is a far far far stronger coffee that I find harder to work with.
FlavorWest Mocha: not that you asked for a mocha flavor, but the list wouldn't be complete without it. By itself, reminds me of hot choc with a splash of coffee. Add NF Organic Coffee, and it's my ideal mocha. I add a little EM (I forget whose "Cotton Candy" I'm using; they're all the same to me), because I like it sweeter. A little Whipped Cream, perhaps?
Although the NF Organics have alcohol, I mix and vape right away without any elaborate steeping rituals. I will admit they both improve after sitting uncapped overnight, but no problem
vaping immediately, and no reason to let them sit out for days or weeks.
You didn't ask for premixed either, but High Desert Vape's Caramelnut Mocha gets my top marks.