It depends on your actual course list. It depends on how much math and physics you have actually taken.
Your biology courses and your technology/engineering courses, they don't have overlap with physics.
If you took math courses, physical chemistry courses, thermodynamics courses, quantum chemistry courses, those overlap. You need a certain amount of ECTS before they will admit you. Take a 180 ECTS BSc physics degree. Strip out the academic skills, the general courses in statistics and whatnot. Take out the thesis. How much credit of core physics ECTS are left? That's what you need, roughly. Say you have 60 ECTS of courses in math/physicalchem/quantumchem/thermo, which is probably very generous. Say the BSc degree has 60 ECTS in broadening/thesis/introductory. Then you have 60 ECTS left. That means a gap year to catch up on core courses. Usually, you will take courses that target a specific specialization in the physics MSc. You won't have the broad knowledge a physics BSc has. Your gap year prepares you for a specific physics track, not for all of them like a usual BSc degree would.
You can also request a transfer to the physics BSc degree. But that may mean you have to throw almost all your biotech ETCS in the trashbin, then start in year 1 of the BSc. Sounds to be way too late for you.
Usually, if you can't bridge the gap in a year, they have you do the entire BSc, including another thesis. If you do a second degree, you need to earn 180 new ECTS points. They can't count double.
Small nuance between a true double degree and a joint degree (though not so small in the time/ECTS difference).
I don't know why you say your only options are environmental tech and MolBio. I think you mean at your current uni, there's just those two master tracks. If you are considering doing another additional 3 years on top of the 5 years you are doing now, plus 4 years for a PhD, maybe also consider changing uni to find the right master track for you and for which you qualify as a biotech graduate.
There is also the option to take physics courses at your current uni. I don't know if you had a free part for a minor, but since you are third year, you are probably doing your thesis and finished with your current coursework. But you can take physics classes. You can do a physics minor on top of your 180 ECTS biotech degree. As long as you haven't graduated, you can take courses as you are still a student there, paying tuition. Unless your uni has restrictions in place.
This may be easier than finishing your degree, then getting the same or another uni to accept you as a new student, not doing a BSc or an MSc, but 'randomly' taking physics courses.
Just make sure you aren't wasting your time getting more physics ECTS. Get in printing that they will accept you when you have a certain amount of physics/math ECTS in your biotech BSc. If not, you may be wasting your time.
Usually, you can take a big minor in physics, maybe do some additional courses on top of the 180 ECTS, do 60 ECTS gap year, and enroll in a physics MSc. You need to get close to 100 or 120 worth of BSc physics courses for them to accept you. But it depends a lot. They may even rule on it on a person by person basis. And it will probably get easier to less prestigious and the less rigorous their program is.
You have been trained as an engineer in biology. But you want to be a scientist in physics. You can also be a scientist in chemistry, a scientist in biology, an engineer in chemistry, a scientist in chemistry and an engineer in physics. Those have all more overlap with what you are doing now than being a scientist in physics.
I don't know if you don't like your current career direction, or that you would rather do something else. But consider the bigger picture. There are many fields and in between them there are interdisciplinary fields. There is biophysics, where your biotech skills help. There is synthetic biology, where your biotech skills help. You use tools from the physics toolbox there, but your research subject isn't other stars or solar systems.
There is also astrobiology, which is usually 'just' the microbiology of extremophiles. If you want to go towards the astro-direction, but use tools from your current toolbox, then you can think about questions/problem in the astro-world using your current degree.Of course when it is clear that you really need to overhaul your education, you should do that. Don't let 2 or 3 years of delay or hard work make you take the wrong career path for the next 4-6 decades.
