For the coffee - I use spenda in my coffee/tea to sweeten it. No calories and tastes just like sugar. If you are only drinking one cup a day, caffeinated coffee would be fine too (they've actually done studies that concluded that the caffeine in 1 cup of coffee was enough to slightly raise your metabolism throughout the day).
As for tea - Green tea is good for you - it has lots of cancer-fighting anti-oxidants. So does white tea, though it's fairly new on the market and is a little hard to find. You could add honey to your tea, but again I personally prefer splenda.
__________________
To be yourself in a world that is constantly trying to make you something else is the greatest accomplishment ~ {Ralph Waldo Emerson}
one cup of coffee, regular or decaf, is fine. whether sugar substitues are healthier than sugar is debatable. if your concerns are health related, i would use a miniamlly processed sugar, like sugar in the raw (they usually have packets of this at most coffee places -- they're the brown ones). if you're trying to cut calories and need sweetener, i think splenda is actually made from real sugar so it's more natural than nutra sweet or something like that.
green tea is very good for you -- it has antioxidants and is supposed to be linked cancer prevention, as well as a lot of other health benefits. (more info: http://www.teahealth.co.uk/th/facts/1.htm) and you can get decaf green tea.
black tea has some of the same health benefits as green tea too, so both are a good choice. and honey is a good choice as a sweetener -- basically, the more natural and less processed something is, the better it is for you, so since honey goes right from the hive to the jar it's pretty good.