Don't turn to alcohol, as it dries out the throat. In fact, better to discover the source of the problem than "cover up" the problem. It's possible diet could be to blame, but you should also look at other allergies. In fact, a visit to an ENT (ear, nose, throat specialist) may be in order. If you can pin point the allergy, then you can avoid it...thereby solving the problem.
In the meantime, the best thing to get rid of mucus and post nasal drip stuff is a saline solution (salt and water). You can buy over the counter saltine nose sprays, but I find that gargling with salt water works better. What works best, though, is getting a netti pot and rinsing your sinuses with salt water.
Hope this helps,
Kristina
http://voicestudio.kristinaseleshanko.com