1w 445 blue laser/reflection

if I was trying to test which liquid takes away the most power from a laser, could I put the liquid in a glass? Or would that reflect?

Yes the glass would reflect, but so would the surface of the liquid. My advice would be to figure out an angle that will not bounce back into your eye, put your glasses on and in a controlled manner turn it on - you will then see where it is reflecting and just be careful not to cross either of the beams you now have, the one reflecting and the one that goes straight through the liquid. Since the glass will be their for all the liquids it will reflect the same amount, only the liquid will change how much light will get through, so you will be able to see which is absorbing the most light.