This is the regime that I used.
Vodka (A half capful per day for one week): Not as serious " bad effects", but results happened quicker. I assume because the carbon source was already a simple sugar. The corals recooperated withing a couple of days. I did notice a dip in nutrients and no visible effects on water. Skimmer skimmed better as it skimmed out dead bacteria.
Couple of week cool off time.
Sugar (a pinch per day for one week): Took a week to see reults, and all my LPS shrank in, a few SPS stayed out if not slightly fuller, and most of my soft corals closed up. Half of my Zoanthinds closed, most of my Corallimorphians closed, and a few of my soft corals closed. After I stopped dosing, it took another week for them to open back up. No visual effects on water quality, but a dip in nutrients level shows it worked, but at a cost of tank health. Skimmer skimmed slightly better.
Conclusion: Whether it is sugar, vodka, or heck, corn syrup, adding a carbon source can help. But, there is no point in adding this if you can't control your nutrients. If you can control your nutrients, then a carbon source isn't necessary but effective. Extreme caution should be taken. Bacteria growth is limited on food. If you add lots of carbon/sugar and you already have lots of nitrates and phosphates, you could have a bacteria bloom, cause your water quality to fade, deplete all oxygen, and crash the system. If you are doing this for sole source of nutrient control, it is a bad choice with many risks. If you are using it to help aid other forms of nutrient control, it can be beneficial in increasing bacteria populations which can in turn help feed Zooplankton populations. If you choose not to do it, then you are no worse for wear.
I would like to compare Vodka with BioBalls. They have their time and place and aren't always the right choice for every tank. Careful time and consideration should be taken before choosing to dose vodka. If you do, it wouldn't hurt to do some large water changes through the course of the month prior to dosing.