I too have a few carts that have just started to run dry. I don't have any nic juice yet (some on order), so I hit up hobby lobby for their (limited) flavor section in the cake decorating section. They had a 60mL bottle of Wiltons(tm) glycerin for $1.99 and some 3.7mL Lorann flavorings, 2 bottles for $2.10.
I picked up some cherry and english toffee. Everybody here on the forum says to use zero nic when you start DIY anyway, so I figued the worst I could do is hoze a few used carts.
While the english toffee isn't "candy sweet" I will say it is very tasty, has great flavor on the exhale. I didn't even have a bottle for my first test, just put 6 drops of Vg into a cart condom with 3 drops of toffee. I had an eye dropper, so popped the top off the cart and dropped it in while holding the cart tilted. A good t-spin and let it sit for at least an hour (more if you can stand the wait).
If you like toffee/butter rum type of taste this is WONDERFUL! With the VG you get really good vapor quantity, for me it makes up for the total lack of nic.
Same for the cherry I had, 6 drops (from an eye dropper) of VG to 3 drops of flavor. Great cherry flavor, but I'm not sure this would give you the 'sweet' you are hoping for. I was quite impressed how a $7.00 investment is helping me build a nice collection of "pacifier" carts I can vape away on between "real" nic hits. Several have been refilled with this same mix 3x so far, just need to watch out for the burning taste. As soon as you even get a HINT of that, stop using the cart an refill.
Please note, I too am a newbie (still posting here cuz I can't post anywhere else yet even). I'm sure alot of my experiences would be called into question from other more aged members of the forum, but at least I'm not messing around with 36mg nic or anything crazy like that!
Happy vaping!