Ejaria arrived at Anfield in 2014 following a nine-year stint in Arsenal's youth ranks, and was handed his senior debut in the 3-0 EFL Cup win over Derby County two years later.
Having been restricted to the odd first-team outing since then, the England Under-20s World Cup winner will now link up with Sunderland to gain further experience in the second tier.
Speaking to his new side's official website, Ejaria said: "I'm really happy because I've wanted to go out on loan for a while to get regular first-team football under my belt.
"I'd say that I'm a player that likes to get on the ball quite a lot and make things happen, I'll try to create chances and hopefully score some goals as well. I'll always give 100% and work hard for the team."
Ejaria was used twice from the bench in the Premier League for Liverpool last season, totalling six minutes of action.