The Trust upheld appeals by ITV and RadioCentre, which both lodged complaints about the BBC's 2007 Sports Personality awards in December last year on editorial and fair trading grounds.
They also alleged breach of the charter and the BBC's Framework Agreement.
The event, which was sponsored by 's Robinsons brand, was broadcast on December 9 on BBC One and Radio 5 from the NEC in Birmingham. There was also coverage on .
The Trust found that the BBC's editorial guidelines had been breached for reasons including the prominence of the Robinsons' logo as part of the set within the programme and the number of mentions of Robinsons during the BBC programmes on TV and radio.
The Trust said in a statement: "The [Sports Personality] programme and website compromised the editorial integrity of the BBC by giving the impression that (via a programme) part of the BBC service had been sponsored."
The BBC is allowed to accept sponsorship finance for BBC events but broadcasts may not be sponsored. Therefore, anything that creates an impression that a programme may be sponsored is "wrong and contrary" to the BBC's editorial guidelines.
The Trust also concluded that there was a technical breach of the BBC Agreement because the BBC did not have an approved statement of policy for the use of alternative finance at the time of the programme. Such a policy is now in place.
Sports Personality of the Year 2008, which is due to air this December, is not to be broadcast as a sponsored event, unless the BBC brings the programme into accordance with the Trust's findings.
The BBC must therefore review its contract with Britvic and ensure that it does not give undertakings about on-air credits, that the coverage of the signage at the event should be appropriate and that any links between the BBC website and Britvic's website should also comply fully with the editorial guidelines.
Beyond the Britvic contract, which ends this year, the BBC is not allowed to seek a further sponsor for the Sports Personality event.
The Trust said that this decision "does not imply any wrongdoing or fault on the part of Britvic Soft Drinks or its Robinsons brand".
The Trust has asked the director-general Mark Thompson to submit proposals for a revision of the editorial guidelines for sponsored events by October 2008 to ensure they are more tightly controlled.
The director-general has also been asked to present a complete account of all the uses of alternative finance sourced from third parties by the BBC. In the meantime, no new sponsored events are to be created by the BBC.
He must also send a written apology to both ITV and Radio Centre.
The Trust intends to publish the director-general's proposals for revised editorial guidlines for sponsored events in due course.
An ITV spokesman said: "We are delighted that our complaint has been upheld following the BBC Trust's conclusion that editorial guidelines were breached and the editorial integrity of the BBC compromised in relation to Sports Personality of the Year 2007."
Andrew Harrison, chief executive of RadioCentre said: "We are pleased that the Trust has responded so positively and quickly to the appeal we lodged following a long engagement with the BBC management complaints system.
"We welcome the Trust's decision to uphold our complaint about sponsorship of Sports Personality of the Year and look forward to the outcome of the wider review of sponsorship of BBC events."
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