Sirles most recently was with the Panthers. Carolina placed Sirles on injured reserve during final cuts but released him with an injury settlement Sept. 6.
The offensive lineman has appeared in 30 career games with 15 starts. Fourteen of those starts came with the Vikings the past two seasons.
The Chargers originally signed Sirles as an undrafted rookie in 2014. They traded him to Minnesota for a sixth-round pick in 2016.