Kirsten Otchere opened the scoring for Leicester City U21s inside just four minutes at Eppleton Colliery Welfare Ground, although Tom Proctor levelled for the the Black Cats just midway through the half.
The home side were in front at the break as well through Jack Whittaker before a second for Proctor gave Sunderland a commanding lead early into the second period.
Brandon Cover's effort got the young Foxes back into the contest on 53 minutes, but we weren't able to mount a comeback. Now seventh in PL2, it's Norwich City next up at home on Monday (7pm GMT kick-off).
The details
City: Donohue; Cover (Omobolaji 70'), Ali, Khela (Hutchinson 82'), Amartey; Motsi, Golding (Fisken 56'), Neale; Briggs, Donnelly; Otchere.
Subs not used: Marson, Linsday.
Goals: Otchere 4', Cover 53'.