A little less than plain, because of the cream
A Grande Vanilla Sweet Cream Cold Brew carries 185 mg of caffeine: 145 mg in a Tall, 185 mg in a Grande, 275 mg in a Venti, and 315 mg in a Trenta. That is slightly below plain Starbucks Cold Brew at the same sizes (155, 205, 310 and 360 mg), because a float of vanilla sweet cream takes up room in the cup that would otherwise be more cold-brew concentrate.
It is well below Nitro Cold Brew, which is not cut with cream or much ice and carries 280 mg in a Grande, the most concentrated cold coffee on the menu.
Same base as the seasonal Pumpkin Cream version
Starbucks’ Pumpkin Cream Cold Brew uses the identical cold-brew base and matches this drink’s caffeine exactly at every size; only the topping (pumpkin cream instead of vanilla sweet cream) differs.
Asking for light cream, or no cream at all, brings the drink closer to plain Cold Brew’s higher figures, since less of the cup is then taken up by the sweet cream float.
Where it fits in a day
A Grande (185 mg) stays just below the 200 mg EFSA assessed as a safe single dose for healthy adults, while a Venti (275 mg) goes past it. A second Grande brings the day to 370 mg, 30 mg short of the 400 mg the FDA cites for healthy adults. Against the 200 mg daily ceiling ACOG uses in pregnancy, a Tall (145 mg) leaves only 55 mg.