I have been very thirsty lately. I drink a lot of water, but all that quenches my thirst is flavored beverages. Could this be diabetes?

Maybe. The term to describe this is polydipsia. It's usually a symptom of something else. Both type of diabetes can cause polydipsia (diabetes mellitus and diabetes insipidus). There are other causes for polydipsia as well. If this continues, see you doctor for a blood test to confirm/refute the diagnosis and find out what exactly is wrong.
Diabetes is possible. Thirst, increased urination, increased appetite are symptoms of diabetes. The diagnosis of diabetes is more likely if you have risk factors: family history, overweight, not active, eat poorly ... You can see your physician and order fasting blood sugars and if >125 diabetes is diagnosed. 'pre-diabetes' is a fasting blood sugar between 100-125 and many people fall into that group.