In 2022, the population of Sinai was 99, a 2.06% increase year-by-year from 2021. Previously, in 2021, Sinai's population was 97, an increase of 1.04% compared to a population of 96 in 2020.
The median age in Sinai, SD is 24.7, as per 2021 ACS 5-Year Estimates. Of the total population, 35.58% were under the age of 15, 20.86% aged 15 to 29, 33.13% aged 30 to 64, 6.13% aged 65 to 84, and 4.29% were 85 years of age and older.