I've had that problem before. There's lots of contributing factors and lots of solutions so I'll sum up a few good ones. I know you are aware of most of these but I'll elaborate a bit.
I've had flavors go sour on me. They're stored indoors, out of the sun at a temperature of around 70 degrees Fahrenheit. They even smell funny, and I've had other people smell them and ask their opinion. Nope, smells nothing like such and such.
Drinking water helps for some.
Others recommend brushing your teeth, and using
Biotene mouthwash. Some even say it's the toothpaste causing the bad flavor.
One person was told by his doctor to chew up some
tums because he complained of a metallic taste.
I can't find a source anywhere and it's driving me crazy, but I read somewhere (I may be crazy) that a certain brand of toothpaste was notorious for making everything taste bad and there was even a lawsuit about it. I did a search for everything I could think of on here and google and came up with nothing.
:shrug:
ETA: The links aren't advertisements, they're links to posts here on ECF validating the claims
