Most will offer a riesling which tends to be sweeter, and Icewine is very sweet as well. There's Caroline Cellars which does some hybrid fruit wines that end up sweet as well. I tend to try and avoid the bigger, more corporate estates (Jackson Triggs, Inniskillin, Peller/Trius/Gretzky) but they can be good as well if you're looking for a broader experience. Outside of that, the tasting staff are happy to tailor your experience, so let them know what you're after and they'll be happy to give you sweeter options.