Guess what I found out by reading the Wikipedia page? It is neither, technically, since it is an acronym. S.I.N.A.R. = science, industry, nature, architecture, and reproduction.
That sounds like ENGLISH to me...unless the words for science, industry, nature, architecture, and reproduction all start with the same letters as they do in English in either German, French, or Italian. Since these three languages are common in Switzerland, not to mention English, who the hell knows how it is pronounced?!
If you maintain that since the words used for the acronym are English words, then it could be pronounced any way it could be pronounced in English. Crap!
My best guess would be to apply the German pronunciation, since the inventor has a very German name: Carl Hans Koch (though Carl with a C instead of a K). In that case, it could be like Sin-are or See-nar...but definitely not Sy-nar.