Dumbarton were on the end of a 4-0 defeat against Hearts this evening.
Two first-half goals from Lawrence Shankland and Michael Steinwender set the hosts on their way before Alexandros Kyziridis and Claudio Braga added further efforts after the break.
Son’s best chance came in the opening stages of the second period when Scott Tomlinson hit the woodwork.
Dumbarton’s Premier Sports Cup campaign concludes on Saturday when they face Hamilton.