Water may be tasteless, but many people find tap water more palatable if placed in fridge to cool and / or add some slices of lemon or lime to jug, which adds virtually no calories nor carbohydrate, just a nice taste.
I think it depends where you live.
London tap water is far from tasteless; it tastes like drinking from a swimming pool, and I for one can't stand the stuff even if thoroughly chilled.
😱 Fortunately, a simple charcoal filter will remove nearly all the chlorine, and one can buy a 1 litre water bottle with such a filter built-in (£10 for the bottle and the first filter, £6 each for replacement filters, the last time I looked). For household use (such as to improve the taste of
hot drinks whilst slowing-down the furring-up of your appliances) I use a Brita Maxtra filter.
No-one has mentioned don't drink too much 'diet' drinks as they contain artificial sweeteners which may cause tummy problems.
Actually, as DeusXM said, drinks tend not to be sweetened with polyols (which are used mainly where a bulking agent as well as a sweetener is needed, such as in sugar-free pastilles) but with sweeteners such as saccharin or aspartame, which don't cause problems (ignore the nutcases who claim that they cause everything from cancer to nuclear war; if there were any truth in that, I would have dropped dead about 10 years ago).
However, one of the more common sweeteners is aspartame - there is a medical condition called PKU, and people with this condition can't ingest aspartame.
This is one of the nutcases' arguments; they scream that "aspartame contains phenylalanine! Phenylalanine is a neurotoxin!!!" — whilst carefully omitting to mention that phenylalanine is a neurotoxin
only to those unfortunate few who suffer PKU (to the rest of us, it's an
essential nutrient); or that PKU is extremely rare (with an estimated only 1 in 100,000 sufferers).