I gave up diet drinks years ago because I came to consider all artificial sweeteners toxic. There are lots of alternatives--the most obvious being water. In the winter, I drink hot tea, herbal tea (best made with fresh herbs), hot water with a splash of Angostura bitters or a squeeze of lemon, or the occasional cup of warm milk with a grating of nutmeg. In the summer, I keep a pitcher of water in the fridge, flavored with slices of cucumber, lemon, lime, or orange. I chill herbal teas and unsweetened ice tea. I also like a splash of bitters in sparkling water.

I have an herb garden, which makes it easier (and more interesting) to make herbal teas. I especially like spearmint, peppermint, lemon verbena, and anise hyssop. Lemon balm (melissa) has a sort of Lemon Joy character, so I only use it occasionally for a hot tea (but it's a great filler plant in the garden). Catnip is kind of grassy, but it's nice for a change. I don't have chamomile, so I use commercial chamomile in the winter.