Well I've never vaped it, so I can only help you from an investigative perspective. What I know -
Halo uses Totally Wicked flavors(fact), and also uses FlavourArt flavors(opinion).
Most people describe the apple in Midnight Apple as 'sour'. Totally Wicked sells a Gold Standard flavor called "Wood Apple" with the description 'A woody sour apple, an acquired taste, reminiscent of homemade scrumpy cider'. I believe this is the apple base.
There is a possibility that you can no longer acquire the
tobacco that they're using, as Totally Wicked had pulled down all of the
tobacco flavors that Halo uses (probably paid off to do this).
However, I think that if you get the right apple base with the right PG/VG ratio (I think Halo uses 60-70%PG), than the
tobacco taste you can customize/modify to suit your tastes.
Quick Edit - And I believe you need a sweetener. Imo, Halo uses Vanillin + a sweetener to sweeten their juices, as some blends have a pink/red hue to them which Vanillin brings. Try adding 1.5% Vanillin and 1% sweetener of your choice to the blend.