Three water cannon bought by Boris Johnson for a total of £200,000 - which Theresa May later blocked authorities from using on medical grounds - will be sold by Sadiq Khan.
The Mayor of London will use the money raised from the sale on youth services, Khan said during his first State of London debate.
"One of the deals Boris Johnson managed to do with the Germans was to buy three water cannon. What I'm going to do is sell them and use the money for youth services," said Khan.
"This shows the inability of Boris Johnson to get a good deal. Second hand, paid almost £250,000. We're paying for storage facilities for these water cannon. That beggars belief."
The cannon were requested by Scotland Yard following the London riots, but 12 months after purchase it was decided they would be too dangerous to use. They've since been stored at a Metropolitan Police training facility and used for training purposes.