Here's the recipe: Homemade Bee Healthy by Jim Withers
5 cups water
2 1/2 pounds of sugar
1/8 teaspoon lecithin (used as an emulsifier)
15 drops spearmint oil
15 drops lemongrass oil
Bring the water to a boil and integrate the sugar until dissolved. Once the sugar is dissolved, remove the mixture from the heat and quickly add the lecithin and the essential oils. Stir until everything is evenly distributed. This solution should have a strong scent and not be left open around bees. Cool before using.
When I use this mix I put about 1 cup of it into one gallon of 1 to 1 sugar syrup. The recipe makes about 1 gallon of mix so will last through 16 gallons of sugar syrup. Oh, and it only costs a few bucks compared to over one hundred dollars for commercial honey bee healthy.