This article is from the Solid Food for Infants FAQ, by David M. Poduska poduska@cis.ohio-state.edu with numerous contributions by others.
How about WATER!? I would be very hesitant to let any kids near diet soda.
Neither saccharine nor aspartame are recommended for young kids (or anyone
else).
As for solids+liquids: Baby fruit/vegies have a lot of water in them and
many kids won't need a drink along with them. However, once you start
with less moist foods (pureed meat/chicken, less diluted cereal), it may
be necessary. Often a kid will reject the spoon after several bites and a
little sip will get the ball rolling again. Take your cues from the baby.
 
Continue to: