Leeds were facing defeat after Paddy McNair broke the deadlock shortly after half-time but Hernandez came up with his ninth goal of the season to secure a point.
The Spaniard has done his best to carry United during a woeful second half of the season, which has seen the club win twice since Boxing Day, and a deft curling finish on 72 minutes sent Sunderland a step closer to relegation.
Berardi, however, was dismissed for a foul on Callum McManaman in the last minute of the game, invoking a suspension which will end his campaign.
Both sides struck the woodwork in the first half but United fell behind shortly when McNair rifled in from close range as Paul Heckingbottom’s defence, including 20-year-old debutant Paudie O’Connor, froze and allowed him to ghost into the box.
Hernandez’s reply gave Leeds hope of a win and after Sunderland’s Ashley Fletcher was thwarted by a superb late save from goalkeeper Bailey Peacock-Farrell, Samuel Saiz saw a last-gasp free-kick crash against a post.
The visitors were desperate for a result, lying seven points adrift of safety after one win from 12 games and pushed closer towards the drop by Barnsley’s win over Sheffield United at lunchtime today. Much of the early stages of their meeting with United smacked of a general lack of form and quality.
Leeds’ initial opportunities were no better than a header from Pierre-Michel Lasogga which flew high over Sunderland’s crossbar and a cross from Hernandez which eluded Lasogga and Gjanni Alioski at the far post.
Sunderland tried to catch United on the counter, using the pace of one-time Leeds transfer target Fletcher, but a defence including 20-year-old debutant Paudie O’Connor kept him largely in check.
Leeds, however, came to life on 19 minutes as Ronaldo Vieira broke into Sunderland’s box and smacked a shot against the face of a post and Hernandez was denied soon after when Camp turned his volley inches beyond the far post with his knee.
Sunderland’s clearest openings fell to McNair and Aiden McGeady, both of whom were denied by saves from Bailey Peacock-Farrell, before Fletcher rose to nod a 41st-minute corner from McGeady against the top of the bar.
Chris Coleman’s side, however, forced the opening goal three minutes into the second half. A clever pass from Donald Love, chipped over United’s defence, found the run of McNair who smashed a rising finish into the roof of Peacock-Farrell’s net.
Leeds struggled to recover from that blow and Sunderland continued to threaten on the break. McNair fired a shot into Peacock-Farrell’s arms while a sliding block from Alioski on 70 minutes stopped McGeady sliding an effort inside the far post.
Alioski could have levelled when Kemar Roofe, thrown on as a substitute, laid an inviting pass at his feet, only for Alioski to lash his effort into the crowd, but Hernandez levelled 18 minutes from time with a classy effort.
The midfielder took up possession in the area and forced Love to back off before curling a deft strike beyond Camp and into the far corner.
Sunderland rallied again and Peacock-Farrell reacted brilliantly to tip Fletcher’s 77th-minute header over the top and McNair then found the hands of United’s keeper with an unmarked strike from 12 yards.
Samuel Saiz, though, could have won the game five minutes from the end when Camp dived at full stretch to turn away his goalbound attempt and an 89th-minute free-kick from the Spaniard rattled an upright before Berardi was shown a straight red card for fouling McManaman.
Leeds United: Peacock-Farrell, Dallas, Jansson, O'Connor, Berardi, Phillips (Roofe 65), Vieira, Alioski, Hernandez, Saiz, Lasogga (Ekuban 79). Subs: Lonergan, Anita, Pearce, Nicell, Ekuban, Grot.
Sunderland: Camp, Love, Kone, O'Shea, Wilson, Cattermole (LuaLua 90), McNair, Honeyman (Ejaria 84), Gooch, Fletcher, McGeady (McManaman 89). Subs: Steele, Matthews, Asoro, Clarke-Salter.
Referee: Jeremy Simpson (Lancashire)