To make glass read as glass, emphasize its edge reflections and specular highlights. Glass usually looks convincing when it has bright, clean highlights along the contours, so use 2–3 large diffuse light sources and position them to define the bottle’s outline.

If the interior paint still lets some light through, try backlighting or letting light pass through the bottle to show translucency. Even a small glowing source behind it can help separate it from plastic.

Other cues can also help: if appropriate, putting liquid in the bottle can create refraction/magnification effects that people strongly associate with glass. Very soft, diffused lighting is generally better than harsh direct light.

If you want to go deeper, lighting glass is a classic studio-lighting problem; books like Light: Science and Magic are often recommended because they explain how reflections define transparent subjects.