There is an onion wine recipe in The Joy of Home Winemaking, and she usually always gives how much sugar or honey is needed for the recipe. Then again, I find a lot of her recipes to follow the unoffical 1-2-3 rule - 1 gallon of water, 2 lbs of sugar, and 3 lbs of fruit.
I make a garlic jam or jelly, which my mother loves and puts on meat, which could also be a good use for a garlic mead. I haven't done it in a while, but basically, I think I use 1/4 cup garlic for one batch, following the directions for the pectin on how much water and sugar. Really, I make a tea with the garlic, and either I strain it out or leave it depending on my mood and who is going to eat it.
Edit PS - I also am in the process of making a bell pepper/peach wine, and I make a mean jalapeno guava margarita.