I digged further into this spray. Apparently its intended usage is use it on clothes before you put it on. Not using it while wearing the clothes (now you're spreading alcohol on your body, not very safe)
After some try and error, I think 4.8 g L-Menthol disolved into 60mL of 95% ethanol, then diluted with 40mL of water is a acceptabled recipe. I feel no different with the original one. You may use 5g L-Menthol if you think it's not strong enough. For coating the cloth with menthol (so you can feel cool when you start sweating), I think you can use less ethanol as long as the menthol don't precipitate out.
If you intent to use directly on your skin, you may lower the amout of menthol and add a bit more ethanol. Too much menthol feels like buring (your skin think it's too cold), and the evaprate of ethanol will actually cool your skin.
However, I do want to mention that you should not solely rely on this spray to cool your body. Only the alcohol is cooling your body physically. The menthol is tricking your skin to think it's cold, but actually not.
I don't know if this will trick your brain to stop sweating and eventually lead to a heat stroke. So please use with care.
I always keep a fan blowing air to me when using this spray. To ensure I won't overheat.
