/diy/ - Do It Yourself

do cheaper plastic coolers generally have a filled core or just an airgap? i have pic related (30 bucks at sams, qualifies as pretty cheap imo) and i want to insulate it more and was thinking of poking a few holes and filling it with expanding foam. would this even be effective? is there a better way? i dont want to put styrofoam inside the cooler or anything that would decrease the internal volume. it also needs to stay portable so no duct taping insulation to the outside.