Well, it looks like you are so eager to make yourself more attractive, especially your eyes right? Sure, it would be best not to use artificial products anyway, since there are always side effects around here. So, my suggestions for you is to keep a lovely hairstyle, also, remember to get enough sleep which would make you look good. Better yet, try to wear contact lenses, which are able to make your eyes appear charming and bigger.
If you don't want to make up but want to look shiny of your eyes, you can wear contact lenses that can help make your eyes look bigger, brighter and shiner etc. Of course, it is depend on what colored or what type of contact lenses you choose. You'd better choose the colors that the most approximate to your eye colors. Hope this help you.
As far as I am concerned, there are three ways for to make your eyes look more shiny without makeup. First, you can use whitening mask and cleaning mask once every week. When you look off color, your eyes will not appear vigor as well. So taking care your face will help your eyes look shiny. Second, the reason why your eyes don't appear vigor is maybe because you have bag eyes or there is too much melanin around your eyes. To solve this problem, you should smear sun cream on your face and use some whiten eye cream to get rid of eye bags or melanin when you go out. Third, you should have good habits such as getting up early and going to bed early as well, avoiding eating cold drink and son. I must remind you that it is a long run for you to have a shine eyes. When you really take care of your skin, you gains. Taking care of yourself is the best solution.
If you want to make your eyes look shining without make up, you can use to wear the contact lenses. I think the colored contact lenses may let you get that effect more. You could have a try. Basing on your original color of eyes, you may choose the suitable colored contact lenses to make your eyes look bigger and shining.