Brendan Rodgers’ side found themselves a goal down when Lars Stindl thumped home a volley in the first-half, but the Hoops fought back strongly after the interval and levelled with Moussa Dembele’s 16th goal of the campaign via the penalty spot.
And Sinclair, who hit the inside of the post with a wicked curling first-half effort with the tie goalless, felt his side have what it takes to compete in Europe.
He said: “It’s still there, I think we’ve got to have that belief and I think we do have it in the team. We are going to keep fighting on until the last game.”
The performance showed a marked improvement from the last time the two sides met when Monchengladbach won 2-0 in Glasgow a fortnight ago.
Sinclair added: “From the first five minutes, you could see the energy, aggression and the way we pressed.
Reflecting on his effort which clipped the post and stayed out the 27-year-old said: “It was one of them days.
“My shot obviously didn’t go in. When I struck it I hit it cleanly and I thought it was going to go past the line, but it didn’t.
“We had a lot of chances in the game, and, hopefully, we will put them away in the future.”