Some good tips here. One more for you.
buy some sweetener and some menthol flavor - either from the link posted earlier or MBV or wizardlabs or somewhere. With just these two flavorings, you'll be able to make almost any juice vapable. Just add a drop or two into the 15ml bottle, shake and vape.
I've managed to save a lot of frankly disgusting juice just using those two flavorings.
Looks like you beat me to my usual recommendation of adding menthol! Yeah, I've saved plenty of juices by adding a few drops (or more, if needed) of menthol, sometimes I just totally mask the flavor with menthol and use it in a pinch, other times it turns out tasting good.
Another tip, if you like cherry candies, or cinnamon red hots, go to Wizard Labs and get the LorAnns Cherry flavoring and/or just about any DIY cinnamon flavor (some sell a Red Hots imitation that happens to be obscenely strong, works great for this but isn't usually safe for plastic tanks). Mix that in at three-five drops and try it. The LA cherry was so strong to me that it quickly became a 'fixer' flavor rather than something I'd vape normally.