From here

Finally playing with SoL in our 1.7 custom pack. Gregtech has a way of making bottled drinks, but they have no diminishing returns. For example, he has a 'Purple Drink' that gives 3 hunger and 1.5 saturation (and slowness debuff)...but has no dim returns. Wonder if there is anything that can change/fix this on your side.

Oh just made a post about that on the Minecraft forum.

http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/2091809-the-spice-of-life-encouraging-dietary-variety?comment=145

Have the issue too. Using GregTech and SpiceOfLife for Minecraft 1.6. I would love if the Purple Drink could be added to SpiceOfLife :)

I find the Purple Drinks as dungeonloot, so its alittle OP to get that, where SpiceOfLife those not recognize it.

Closing. This is no longer an issue in 1.7.10 and I've finally started dropping support for 1.6.4.