Is it true that there is a charge for water during dinner?
No, but there is a charge for bottled water because it's a bar beverage.
Note that there's no reason to buy bottled water aboard ship. The water from the ship's distilling plant is far more pure than both normal drinking water ashore and nearlly all bottled water, regardless of the source.
Can I bring bottled water/soda onboard ?
Sure, but it's much easier -- and cheaper -- to buy a "soda sticker" if you drink a lot of soda. Once you have a "soda sticker" on your cruise card, you get free foundain sodas from all bars on the ship for the duration of the cruise.
There is no charge for tap water, the charge is for bottled water.
Ships water is very pure and very good. What we do is to buy a few sports bottles of water at the grocery store before we board, and then we re-fill them from the tap and chill them.
If you drink more than 2 sodas per day it is worth it to get the soda sticker. A soda on board costs around $2.50.
The sodas on board are Coke products. IF you must have something that is not a Coke product you can bring aboard a 6 pack and then replenish on the islands.
I look for the water coolers since they have filters on them. Sometimes the tap water has a bit of color in it . . . I've asked the enviro officer and facilities managers on several ships. The color is just minerals - but I like the filtered better. Anything that serves water (self serve beverages, coolers, ice machines) have filters on them that are changed regularly.
There's always a late night line up at the water fountains in crew area - liter bottles, 1 gal containers . . . some ships even put a spigot just for this reason on the sides of them!
One of the filter manufacturers makes a travel or sports bottle with a filter included . . . Brita?
whatever deck (1 or 2) that you debark on for docking - keep an eye out . . they're usually within eyeshot of the closest bathroom. I don't think you can (or should) refill directly from Windjammer taps, you might have to use a cup or glass to transfer!
and for those who still want to buy the traditional bottled water . . . just bring along enough to get you to the first port, then ask your room attendant (or any other friendly crewmember) where the grocery stores are! (as long as the first port isn't CocoCay or Labadee ;-)