//EDIT: I wasn't too happy that the light gets scattered in my material so there are no sharp shadows inside the bottle. In the other answer the black edge bothered me, which won't go away no matter how high I set the bounces. But I found the problem. So here at first the most simple setup which also renders a bit faster than the improved setup, which you will find further below.
Simple Setup: I downloaded your file and made the material setup a little bit easier... a quite good glass material is actually the Glass BSDF. To keep it from looking too dark you have to do two things:
- Make it completely white with R/G/B = 1/1/1.
- Increase the bounces of not only Transmission, but also Glossy (and then of course the Max bounces or Total in newer versions, because they limit them overall).
So this is my material setup (this is from my Blender 3.1 version, but the render below I did with 2.79):
And this is the render result with the following bounces settings, Max: 32, Diffuse: 4, Glossy: 32, Transmission: 32, Volume: 0.
I think this looks quite okay. You'll never get rid of some of those dark areas, since there are objects with shadows which also get reflected and refracted. The crucial thing is, many people just crank up the Transmission bounces because they think, darkness in transmissive things only comes from too few bounces there. But since the glass is also glossy, those bounces play a role that's not to be underestimated.
Improved Setup: The solution to get sharper shadows inside the bottle from outside lights is a setup which is close to the answer from @mqbakamqbaka - the dark edge which bothers me is caused by the Is Reflection Ray light path. To get a better result, use Diffuse Depth instead:
And this is the new result, I still used the Glass BSDF, you can use a Principled BSDF - that doesn't make much of difference. Only that the Principled BSDF gives a slightly darker result, but it doesn't look more or less realistic than the Glass BSDF. The only thing I experienced (on my PC) is that in 2.79 the Principled BSDF renders faster than the Glass BSDF while in 3.1.0 it is the other way round.
Another thing: if this result seems to be too bright inside the bottle (since no real glass lets 100% of the light pass through), you can always place a Multiply node after the Maximum node to multiply the result by some value lower than 1, which works like mixing between the simple glass material if you multiply by 0 and completely improved material at 1.