Make lemon syrup by combining hot water, sugar and lemon juice.
When syrup is cool, make drink by combining 3/4 ounce lemon syrup with citrus, vodka, limoncello, lemonade and 1 cup of ice in a blender. Blend on high speed until ice is crushed. Add additional ice, if needed, to make drink slushy.
Serve in a 16-ounce glass with a straw and a thin slice of lemon on the rim of the glass.