During my 15 years as an auto mechanic, I tasted antifreeze many times
and can attest to the fact that it is indeed VERY sweet tasting.

Somehow I am not surprised to hear that.  They don't jump for
lollipops, you'll notice.  The only sweet things that cats crave are
usually loaded with milk, and *that* is what attracts them, not the
sweet taste.  Try putting honey on your finger and you'll see.  Pure
sugar, no milk, no dice.  Macaroni & cheese, real milk in it, no sugar,
devouring lion behaviour.  Not that I am recommending a regular diet of
mac&cheese, but just making the point.

There *is* something, by the way, in the taste of antifreeze that
attracts cats, but it is not sugar or any type of sugar compound, it is
ethylene glycol.  Well, there is a very, very, distant connection with
sugar, but not that the taste buds would notice.  I think we have
historically said it tastes sweet to the cat to imply that the taste
attracts them, but not that it is actually sweet, as in, containing
sugar.

And, to echo the earlier response, you do not need to increase or
modify your cats drinking behaviour, on the whole, when their own
metabolism tells them exactly when they need to drink.  You just need
to have clean fresh water available 24/7.  If you started adding stuff
to the water, you could end up screwing up their thirst mechanism so
that they will not, in future, recognize the symptoms of dehydration
and respond knee-jerk-wise by going for water or wet food.  Best leave
well enough alone, I say.

--tension

I made a fountain out of an old 2 qt. saucepan and a small pump which
shoots the water about 2-3 inches into the air.  This provides some
noise and motion which makes the cats want to play with the water.
The water where I live (Eden Prairie, Minnesota) is very good; I drink
it right out of the tap with no additional processing.
Also, when in the fountain, I think the circulation and exposure to
the air gets rid of the chlorine fairly quickly.