I would say most Swiss drink a combination of tea, coffee and water on a regular basis.
In the Swiss German area, coffee is known as kaffee creme for coffee with cream and sugar, and Milchkaffee with fresh milk. Kaffee fertig is coffee with Schnapps.
In Romandie, cafe au lait is the common known coffee with milk.
Tea (Tee, the, te) have a variety of styles much like most of Europe where you have creme or milk in your tea. However, you will find your ice tea (eistee, the froid, te freddo) are all sugary drinks of ice tea.
Water is safe to drink all over Switzerland, whether from taps or from the public street fountains that you see dotted throughout many villages and towns. These fountains almost always gush out pure spring water.
Now if that is hard to believe this mineral water (mineralwasser, eau minerale, acqua minerale), come up to a popular trough to watch all of the locals with many refillable bottles getting their months supply of the stuff for free.
Of course there are just a few exceptions which will always be marked "kein trinkwasser", "eau non potable" or "acqua non potable". Also it is not so recommended that you get water from open streams as they may have been used by the cows in the area.