Our lights have a single LED at the top and we were losing light out through the hole at the bottom of the "globe" and down the tube of the spike.
We took the foil seal from a Maxwell House coffee can and used that as material for a reflector cone to insert at the bottom of each of our lights.
I cut out a circle of foil a bit larger than the circumference of the "globe" and cut a slit from the edge to the center of the foil circle.
I twirled it into a cone shape and placed it in the bottom of the "globe", pointy side up. Thus providing a large reflective surface and also keeping the light from being lost down the tube.
If you have enough foil and patience, you can experiment with the height of your cone for maximum results.
This modification makes quite a difference.
We have three of these garden lights outside the boat. Yes, I know they are not proper anchor lights but I like having lights at deck-ish level. Anything that makes us easier to be seen by boats zipping through the anchorage at night is a good thing. Anchor lights at the top of the mast can be difficult to see against city lights, plus I find it difficult to judge the boat's distance.
We also use one of these as a nightlite in the salon... Just have to remember to put it outside in the morning to get charged up for another night ;)