Sweet potato varieties with orange or red skin and deep orange flesh, including Red Garnet (our favorite) and Jewel, cook up sweet and moist.
For our Best Baked Sweet Potatoes(https://www.cooksillustrated.com/recipes/9903-best-baked-sweet-potatoes\), we recommend passing on tan- or purple-skinned sweet potatoes (so-called dry varieties) and sticking with red or orange, which are known as “moist” varieties. These contain more of the enzyme amylase, which breaks down starches into sugars. This not only makes them taste sweeter but also means that, with less starch to absorb moisture, these sweet potatoes have a moister, creamier texture than the dry varieties.
Side note: Red and orange sweet potatoes are often labeled “yams.” This is a misnomer. True yams are unrelated tubers that are starchier and drier than even purple- and white-fleshed sweet potatoes, with a thick, fibrous skin; they’re generally hard to find in American supermarkets.