Ndungane then scored the first try of the night after catching a cross-field kick from Lambie, who missed the conversion.
Reinach was awarded a try by the Television Match Official in the 29th minute after going over from the base of a demolished scrum, with Lambie adding the extras to put Sharks 15-3 ahead.
Boshoff cut the deficit with his second penalty before the break, with another score 10 minutes into the second half putting the Lions six points adrift.
The fly-half's fourth successful kick put the Lions 15-12 down but Coetzee barged over in the 63rd minute with Lambie slotting the conversion to give the hosts some breathing space.
A try was ruled out for the Sharks when SP Marais was deemed to have been offside, but the Lions' loss of Whiteley a minute later to the sin bin after he tapped the ball out of Reinach's hands led to the bonus point try for the hosts.
A dominant maul from the Sharks ended with Coetzee scoring a second try, with Lambie again on target with the extra two points to wrap up the victory.
- AAP