Appears to be about a deal done in 2015, 2 years prior to Burnham becoming Mayor, and ended last year.
The 'sweetheart' probably doesn't refer to a mistress/girlfriend...
Come on, man...provide something for people to actually refer to?
Is it this?
https://www.thetimes.com/uk/politics/article/manchester-city-council-uae-firm-sweetheart-property-deal-fh8x7b2b8
Watching the Sky Sports News media discussion thing - a number of papers have stories to the effect of "Give it a rest, you've been caught so admit it"