Regular Coke is just unnecessary calories, but I want to drink something other than water. I drink at least 64oz of water throughout the day, and at least another 64oz of soda. I'll give coffee another shot in a few days since I have some upcoming appointments in the next couple mornings and dont want to risk it, but maybe I'll try tea after. But just drinking water all day lacks variety.
Try drinking coffee black next time. Most people don't like coffee black until they've acquired the taste because coffee is usually at least a little bitter black (it doesn't have to be, but the common grinds and methods of preparation often make it so). It helps if you have a good coffee shop or can make it any other way than via drip (e.g. French press/Aeropress, pourover/coldbrew, moka, etc) using the freshest beans and grind possible. Lighter roasts have more caffeine than dark roasts, contrary to common belief.
I love tea (green and black mostly, but occasionally white and oolong) and coffee. Some of the green teas (gyokuro and matcha especially) rival black teas and even coffee in caffeine content, too, and with less caffeine jitter or crash (has something to do with the other stimulants in tea including theobromine, which is also present in chocolate). You get a calmer focus and no laxative effect (the diuretic effect is there, though - you will have to urinate more).
All sorts of origins and varieties for both tea and coffee, and subtle flavors once you get past needing milk/creamer or sweeteners. Both have a myriad of health benefits, too, but adding milk and sugar dampens that. So you are really better off learning to enjoy them without additives, if possible.