Judge Bhunu also said prosecutors had not proved that e-mails allegedly linking Mr Bennett to Mr Hitschmann were genuine.
Mr Bennett's supporters had said the charges were aimed at undermining the coalition government.
A spokesman for the MDC has said the party will push for Mr Bennett to take up his ministerial position immediately.
Although the case was a major cause of tension in the power-sharing administration formed in 2009, several other problems remain, such as nominations to key positions and accusations of continued persecution of MDC activists.
Last week, Mr Mugabe and Mr Tsvangirai put on a rare show of unity to appeal for investors to return to the country.
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