Can drinking Mountain Dew cause it to hurt when you pee?

Sodas can increase. risk for many health issues. But I no of no studies which suggest that sodas would cause pain with urination.
Infection? STD? No soft drink or anything else you eat or drink is likely to cause painful urination. Chemical irritants can do it (like soap if using it as lubricant for masturbation). Or urinary tract infection (rare in men your age) or an STD (the most common cause at your age, if you are sexually active -- especially if discharge also is present. Get care ASAP if it continues more than a day or so.