You need to choose a very dry white wine.
The ideal wine is a Fendant (Wine produced in Switzerland from chasselas grapes). It can also be found under such names as Chasselas, Dorin or Perlan).
If you encounter difficulties finding it (or if it is decidedly too expensive since only imported in small quantities), you will have to do with another type. During my travels abroad, I sometimes bought 2 to 3 different bottles in order to choose the one most appropriate for fondue. In general, I found that some sauvignons blancs (not aged in oak barrels) or dry chardonnays are quite OK. In fact the pronounced character of sauvignon blanc is actually interesting in fondue. Pinot Grigio is also good, but it must be very dry (taste it before using it for fondue).
Avoid at all cost sweet wines and too specific tastes (Gewurztraminer, Riesling, Muscat), but above all:
Fendant from Valais with typical
fendant glassesFendant from Valais with typical fendant glasses
Fendants
Fendants