Having slumped to a shock defeat at BATE Borisov in the Champions League on Tuesday, Bayern barely broke sweat in a tepid encounter at the Allianz Arena.
Dutchman Ibrahim Afellay scored his first goal for Schalke 04 in their 3-0 win over VfL Wolfsburg, who are managed by Schalke's former coach Felix Magath, and Hamburg SV continued their climb up the table by winning 1-0 at Greuther Fuerth.
Mainz beat Fortuna Dusseldorf 1-0 with an 85th minute goal by Macedonia defender Nikolce Noveski to end the promoted side's unbeaten record and Freiburg beat Nuremberg 3-0 to hand their opponents a fourth defeat in a row.
"We dominated the match and prevented Hoffenheim creating any chances," Bayern coach Jupp Heynckes told reporters.
"We were highly motivated and took control right from the start. Once we'd taken the lead, I knew our forwards were always good for another goal."
"Bayern played very well and we tried to defend as best we could," said Casteels. "It went very well in the first half, but at the end of the day, Bayern only needed a couple of chances. We didn't attack enough."
Peru striker Jefferson Farfan struck the first blow for Schalke when he headed in Christian Fuchs' cross in the first real chance of the game after 33 minutes.
Within one minute of the re-start, Afellay, on loan from Barcelona, was sent clear by Lewis Holtby's pass and drilled the ball past Diego Benaglio.
"I enjoyed the match and I think the fans did as well," said Schalke 04 coach Huub Stevens. "I'm happy with the result and the way we achieved it."
