The Dutch took the lead through Robin van Persie's strike but Ivelin Popov equalised just after the break. The visitors then earned a surprised win when Ilyain Mitsanski scored in the 93rd minute following Heitinga's misplaced pass.
Following the unexpected defeat, Van Marwijk pulled no punches in his analysis of the game.
"The last 30 minutes has annoyed me. A pass like Heitinga's is just forbidden. You just don't do that. Now we have lost and that's not good," he told SBS.
Despite the result, the former Feyenoord trainer did take some positives from the fixture.
"I think the first half was quite good, especially in comparison with our last games. We didn't create many chances, but there were some situations where we actually should have scored. The last half hour has ruined everything. We haven't been ourselves anymore," he added.
Mark van Bommel also spoke after the match and admitted the Netherlands were far from their best.
"Nobody likes to lose. I think the first half wasn't so bad, we had a lot of ball possession. But it's important to create chances and we should have done that more often. We weren't very dangerous," the 35-year-old stated.
Netherlands face Slovakia in another warm-up game on Wednesday before facing Northern Ireland next Saturday.