Re: alternative to stimulants?

No. There really aren't any stimulants as I have found myself in your position and have asked that question many times on curezone to no avail. You do have options though, if you cut out meat and sweets from your diet, (perhaps some exercise) you'll require much less sleep. Meat makes people really tired, I know this from personal exp. because it requires a great deal of digestion. Try eating alot of salads and green drinks plus water. You'll have better energy.
Also, there is a healthy alternative to Red Bull's called XS Gear or try Quixtar or xsgear.com. They have energy drinks that come in different flavors and do work to keep you up in the beginning, only problem is that your body develops a tolerance and you end up having to take alot just to get it to work after awhile.
Last resort, you can buy some pure caffeine powder from eBay and mix in your drink and that should work. Tweet