The former Soviet Union started withdrawing its forces from East Germany in December 1988. I believe it was a quarter of a million soldiers that were pulled back. So if they had reversed course in 1989 and invaded West Berlin that would have caused fuel shortages in the Soviet Union for civil consumers of gasoline as all of the Soviet Army trucks would have required fuel.
Pink Floyd’s concert at the former Berlin Wall probably wouldn’t have happened. Instead, Metallica would have been commissioned to perform at the battle-line from the trench-works dug around Berlin to contain Soviet expansionism. A-10 Warthogs would have swirled menacingly around Berlin while vast right-wing fireworks displays followed by oil-based fog from machines would have confused Soviet Red Army forces.
If there were vast concentrations of explosives buried beneath Berlin in case of invasion they would have been detonated creating in effect, a vast sinkhole that eventually would have filled with rainwater and become a fishing spot of note.
Very likely static electric discharges across the sky would have followed a Soviet Red Army invasion of West Berlin. Tremendous Van De Graff field generators with stealth technology and fueled with synthetic cornohal would have been moved under cover of darkness near Berlin and cast crackling power lines over the city before it became a sinkhole. Then, with some softening up, the Meissner field would have taken effect and lifted the city to move it thirty miles west.
The psyops team having completely confused the opposition force would have allowed the decoy, holographic Berlin to remain when the real city moved west. It would have been the fake city of West Berlin that actually followed the sinkhole into the oblivion captured in the term; not a bite all day.