The Black Cats trailed at halftime after Tyrese Campbell’s first-half goal but fought back in the second half.
Eliezer Mayenda leveled in the 76th minute, before Tommy Watson sealed victory with a late goal in the 95th minute.
“It was a tough game. Small details can change the outcome. We kept the resilience and that is one of the main strengths of this team. Even when it is tough and they struggle, they stay connected and they don’t give up,” Le Bris told Sunderland website.
“It is always difficult to make a decision but sometimes it is just instruct. We felt we needed some pace and someone to win their one-v-one and Tommy is that kind of player. He is a good finisher and he shows that this afternoon - we are so proud.
“It will be another chapter next season,” he continued.
“The Premier League is really hard and tough - the most competitive league in the world. We will have another tough challenge but we will see later.
“It is really impressive the way they believed in their dream. The players told me earlier in the season that they wanted to get promoted and they have done it so congratulations to them.