Substitute Bebe arrived at the far post to finish powerfully from a Marnick Vermijl cross at Cape Town Stadium in a game that burst into life in the final five minutes.
Alcardo Van Graan gave the home side an 85th-minute lead with a clever finish from a corner in cold and rainy conditions.
United then surged forward and Bebe kept it unbeaten on its two-game tour of South Africa, following a narrow win over Amazulu earlier in the week.
New signing Shinji Kagawa played 75 minutes in midfield, and sent a second-half header just wide from close range following a cross by Javier Hernandez.