my preferences changed over the years, and even over the course of the day
my first year was mostly water (usually cool or sometimes very cold with ice, depending on the day), or also Crystal Light or sugar free koolaid, but more diluted than recommended, otherwise they were too sweet.
after a year, I added back some carbonation slowly with some Diet Coke and diet ginger-ale or Fresca, but I need to watch the carbonation. I still drink a lot of the Crystal Light and have discovered Hawaiian Punch which is great tasting.
I find water easier early and mid day. Later in the day, it tastes metallic when it hits my mouth.