Mix the yeast with the warm water and 1 teaspoon of the sugar in a large bowl or the bowl of a stand mixer; whisk until smooth. Let stand until puffed, about 10 minutes.
Whisk in the 2 eggs, oil, and remaining sugar until incorporated. Add about half the flour, then the salt; mix into a ball using a wooden spoon or dough hook. Knead until smooth, about 10 minutes, adding more flour as needed. The dough should be soft and tacky.
Place the dough in a warm, cleaned bowl and cover with a towel. Let ferment until doubled, about 2 to 3 hours.
Line a baking sheet with parchment paper. Divide the dough into 4 pieces and roll each into a long rope. Lay 2 ropes vertically and 2 horizontally, weaving them into a tic-tac-toe (#) shape with 8 ends radiating out, which you can think of as 4 pairs. Braid the ends around: take the strand that sits underneath in each pair and cross it over its neighbor, doing one from each side and working around the loaf. Keep going reversing directions each time (the over-under flips each time around) until the strands are too short to cross, then tuck the final tips underneath to form a neat round.
Cover and let rise another 45 minutes, until light and fluffy. Meanwhile, preheat the oven to 350°F.
Whisk the egg yolk with 1 teaspoon water and brush generously over the challah (two coats recommended). Top with sesame seeds or sprinkles, if desired. Bake about 30 minutes, until deep golden brown. Tent with foil if it's browning too quickly on top.
Cool on a rack and serve with honey for dipping. Shana tovah u'metukah!