As Fabulor has been pushing through the 50-60 levels, I've noticed a severe shortage of water. Previously, a more effective type of water was available every 10 levels; at level 25, 35, 45, etc. Fabulor has been dutifully carrying around a stack of the level 45 water - Morning Glory Dew - for a while now, since the moment he could use it.
When Fabulor hit level 55, he visited an Innkeeper to get a new supply of delicious mana drinks, but was surprised to learn that she had nothing new for him! The next available vendor-brought water is Filtered Draenic Water, which requires level 60.
Now, I wouldn't normally care about the 10-level pattern suddenly changing, except for one thing - HELLFIRE RAMPARTS. I know I'll be spending some time in Ramps before I hit 60, and knowing Ramps and its infamous influx of...inexperienced...DK tanks, I have a feeling I'm going to need the water upgrade.
Fortunately, there are a few uncommon beverages that can nicely fill this void! A steady supply of any of these drinks will last you until you hit 60 and figure out how to open the stopper on those crazy Draenic waterskins.
A huge amount of mana regeneration and a small Spirit buff, all at level 45? This drink is amazing! However, it requires Revered reputation with the Argent Dawn, which isn't easy. If you do happen to have the rep, however, then you're laughing - you'll use this all the way until level 60. Costs 60s for a stack of 5 and is purchasable from Argent Quartermaster Hasana in Tirisfal Glades, Argent Quartermaster Lightspark in Western Plaguelands, or Quartermaster Miranda Breechlock in Eastern Plaguelands.
The Argent Dawn takes care of their own, that's for sure. This great food restores health AND mana, is usable at level 45, and only requires Friendly with the Argent Dawn, which is quite easy to attain. A solid contender until you can use the level 60 drinks. Costs 60s for a stack of 5, from the same Argent Dawn NPCs who sell the Blessed Sunfruit Juice.
Another great, low-level-requirement drink option...or is it? Despite only requiring level 45, this water requires Friendly reputation with Thrallmar/Honor Hold, something all but impossible before level 58-59. So that's...weird. And you can't use a higher-level character who meets the reputation requirements, since it binds when picked up. Costs 20s for a stack of 5 from Quartermaster Urgronn (Horde) or Logistics Officer Ulrike (Alliance).
This is an amazing food that will easily sustain you through the 50-60 level bracket. It only requires level 51, restores more mana than Morning Glory Dew, and restores health as well! The only problem is, it's a bit of a pain to acquire. You can buy it in the Hillsbrad Foothills from Jorek Ironside (Horde) or Thanthaldis Snowgleam (Alliance). Alternately, you can venture into Alterac Valley itself (the battleground) and purchase some from Grunnda Wolfheart (Horde) or Gaelden Hammersmith (Alliance), who are both located inside their respective faction's home bases. Costs 70s for a stack of 5.
More nutrition from Alterac! Unlike the Alterac Manna Biscuit, this water only restores mana, but it does give you a short buff to Spirit (like the Blessed Sunfruit Juice). It can be purchased from the same vendors as the Manna Biscuit, as described above. Costs 50s for a stack of 5.
This is my favorite choice, for basic simplicity - you can get this water right in Orgrimmar or Stormwind, from the PVP vendors. Solid mana regen, for the low cost of 12s and 1 Honor Point for a stack of 5. Don't let the PVP cost scare you - a few Honor points are NOTHING. Do a single battleground and you'll be set. Heck, even do a few MINUTES of a battleground and you'll get enough Honor to grab a few stacks.