The Dons have now gone six matches without a win after it had looked as if Michael Smith had provided them with three much-needed points in the final home game of his loan spell from Charlton.
Sheridan said: "It was a great ball from Ben Purrington and fair play to Reuben for being in there around the penalty area and it was a good finish from him.
"I think we deserved something from our second-half performance and we finished the game really strongly.
"When there's two minutes to go and you're 1-0 down it's pleasing when you get something from the game.
"In the first half I thought we were a bit flat against a system I didn't think they would play against us, 3-5-2, and they caused us a few problems.
"We then came out for the second half and were a goal down after two minutes - it was a poor goal and it gave us a mountain to climb.
"But our subs gave us a bit of a spark and we matched their system and we started to get on top of the game towards the end."