The regulator received complaints from viewers over an item on the programme about the benefits of caffeine, which featured the caffeine energy drink Red Bull.
One viewer complained that the item "seemed like an advertisement for Red Bull with celebrity endorsements", while another described it as a "sponsored advertisement for the coffee and Red Bull industries".
The item was broadcast the day after Richard & Judy had transmitted a discussion on the dangers of excessive caffeine intake.
Ofcom ruled that, although the broadcast was clearly intended to make amends for errors in the previous day's programme, "Channel 4 has demonstrated uncharacteristically poor judgment". The ruling added "this culminated in the distinct impression that the programme had come under external commercial influence, giving Red Bull undue prominence".
Channel 4 admitted it had breached the code but it escaped the maximum sanction - a fine of 5 per cent of its qualifying revenue - because of its overall compliance.
In 1994, Granada Television was previously fined £500,000 for product placement during Richard Madeley and Judy Finnegan's previous show on ITV's This Morning.