Do you want to taste it or just use it up?
If you just want to use it, I’d turn it into modified Paloma’s. Mix up grapefruit juice, grapefruit vodka, rosemary infused vodka, and some Angostura bitters in a pitcher and refrigerate. Then to serve, pour the mix into a highball with ice and top with a little grapefruit soda (I strongly prefer San Pellegrino), garnish with a small sprig of rosemary. You might add some sweetener or something to tone it down. You can also make it a little showy by smashing the rosemary sprig with a big flourish and handclap.
I left off portions since I really don’t know what the vodka tastes like. I’d sample it first with mostly vodka and then up the other measures as needed to get something palatable.
If you like egg nog and want to try something kind of similar, try Coquito. It’s spiced coconut cream and rum. It’s got a similar texture without any eggs and a lot of those holiday spices. Here’s a recipe. It can be batched up and stored for a week or two in the fridge.
The other one I like is Amaro Caldo. It’s just hot water and your favorite amaro. I prefer to use tea instead of plain water. A black tea plus an ounce or two of Montenegro is really tasty.