Most people follow the standard route from the Kennedy Meadows trailhead up Night Cap Peak Trail to the summit. That is for sure the easiest route. However, if you are camped at Kennedy Lake and want to bag Night Cap Peak from the south, the route from Kennedy Lake Trail is a viable alternative. Keep in mind that although it is just a scramble up to the summit, this route is entirely off trail and consists primarily of sand and scree. The route follows the drainage on the south side of the peak.
Kennedy Meadows TH to start of route: 4 miles (on trail)
Kennedy Meadows TH to Kennedy Lake: 7.5 miles (on trail)
Kennedy Lake to start of route: 3.5 miles (on trail)
Start of route to summit: 1.9 miles (off trail)
Elevation gain from KL trail to summit: 3000'
Follow the Huckleberry (main) Trail from Kennedy Meadows Resort to the Relief Reservoir / Kennedy Lake trail split (2.5 miles). Follow the Kennedy Lake Trail for 1.5 miles to the beginning of the route, or to Kennedy Lake (5 miles), whichever is your destination.
The route begins from the Kennedy Lake Trail about 1/4 mile east of the Night Cap Peak Trail junction. Follow the drainage due north towards the summit. It is moderately steep in places but it is fairly open country. Just follow the path of least resistance.
Once you reach an elevation of 7900', stay on the west
side of the creek until you are above the bushy zone (about 8400'), as the other side gets cliffy in some spots. There are a few Huckleberry bushes that you'll need to maneuver around between 8000'-8400', but they are not too bad.
Once above the bushes, aim for the saddle between the true summit and the peaklet to the west. You'll find some small-medium sized talus on the upper portion of the route, providing some relief from the loose sand and scree. The final summit ridge is an easy class 3 ascent.
Note that the upper portion of the creek is dry in late summer. However, there is spring fed water flowing in it starting at about 8400', even during late summer on a dry year. I drank directly from it near its source 2 years in a row without getting sick.
No special gear is required for a summer ascent.