I was supposed to practice singing today, but I forgot and ate some yogurt, and I'm figuring that while my voice is blocked, I might as well see if there's anyway to unblock it before I go around singing like I'm gagged.
Water/tea with a little lemon does a nice job. Anything with a slightly acidic content seems to do well.
this sounds very weird but works very well, grab your tounge with one hand and say GAH, GAH, GAH over and over again for about a minute and it will clear up the back of your throat. The more you do it, the clearer your throat gets. It is actually helpful to do this any time before you sing.
You can gently use vocal fry on a low note, then raise the pitch for a while. When you're in vocal fry, your cords are so loose the phlegm just loosens off. After it's loose, just gently cough.