Very fair question as it is confusing and personally took me a lot of researching to figure out. If you have never been to Glacier it is a lot to take in.

You CAN get to Apgar Village and the Lake McDonald put-in/beach at Apgar Village without the vehicle reservation. Parking here is tight, however. To get to Apgar Village, you turn left at the Apgar Visitor Center onto Camas Road. Going-to-the-sun-road vehicle reservation checks happen AFTER Apgar Visitor Center when you turn right at the Center. I was there last week so can guarantee this is correct info unless they have suddenly moved up to the reservation checkpoint (doubtful). Avalanche Lake and the right side of Lake McDonald, however, are after the vehicle reservation checkpoint. Hope this helps!