It had a long vowel in Latin (sīc), meaning that it was pronounced like the English word "seek"; however, it is normally anglicised to /'sɪk/ (like the English word "sick").
The word sic may be used either to show that an uncommon or archaic usage is reported faithfully: for instance, quoting the U.S. Constitution:
The House of Representatives shall chuse [sic] their Speaker...
or to highlight an error, sometimes for the purpose of ridicule or irony, as in these examples:
Warehouse has been around for 30 years and has 263 stores, suggesting a large fan base. The chain sums up its appeal thus: “styley [sic], confident, sexy, glamorous, edgy, clean and individual, with it's [sic] finger on the fashion pulse.”
It is also sometimes used for comic effect:
The Daily Mail was the first newspaper [sic] …It is sometimes erroneously thought to be an acronym from any of a vast number of phrases such as "spelling is correct", "same in copy", "spelling intentionally conserved", "spelling included", "said in context", or "sans intention comique" (French: without comic intent). These "backronyms" are all false etymologies.