There are a number of words that start with the "sah" sound. They're typically words we've adopted from another language, but are now accepted English words. The following are from Merriam-Webster, starting with the comparison word; note that MW provides an audio clip on each page so you can get an idea of how each is pronounced.
saga
\ ˈsä-gə \
sadhu
\ ˈsä-(ˌ)dü \
: a usually Hindu mendicant ascetic
sahib
\ ˈsä-ˌ(h)ib \
: SIR, MASTER —used especially among the native inhabitants of
colonial India when addressing or speaking of a European of some
social or official status
sake (2)
\ ˈsä-kē \
: a Japanese alcoholic beverage of fermented rice often served hot
Certain words starting with sar- that are either monosyllabic or have the stress on the first syllable may have the same pronunciation as the first syllable of saga, depending on whether the speaker is non-rhotic. Candidates include sarcasm, sarcous, sard, sarge, sari, sark, sarmentose, saros and sarsen. One of these is sufficient as an example (again relying on MW's dictionary entry):
sard
\ ˈsärd \
: a reddish-brown variety of chalcedony sometimes classified as a
variety of carnelian