The Bavarian giants won 2-0 in Bremen in the Bundesliga on Saturday, but not before Heynckes had give them important instructions at half-time.
"We slowed things down too much in the first half," he told Bayern's official website. "The players tested my patience a little too much, but at the end of the day, it was enough to beat a strong Bremen side.
"I had to use some strong language at half-time."
The win at the Weserstadion sees Bayern maintain their perfect start to the Bundesliga with six wins out of six.