Put water, sugar, and yeast in the bowl of a mixer, and mix with a paddle.
Add two of the eggs, and the oil, and mix.
Switch the paddle to a dough hook. Add flour and salt, and mix.
Put dough on a floured board and knead. Then spray a large bowl with nonstick spray, and leave dough in bowl, covered, for at least one hour.
Punch dough down, knead again on a floured board. Take half the dough and cut into six even pieces, and roll out each piece into a roll about 12 inches long.
Arrange rolls side by side on the board, pinched together at the top, and braid: Move the furthest roll on the right over 2 rolls, then move the 2nd furthest on the left all the way to the far right. Move the furthest roll on the left over 2 rolls, then move the 2nd furthest on the right all the way to the far left. Repeat until the whole loaf is braided. Then either tuck the ends underneath, or twist into a circle to make a round challah. Repeat with the remaining dough to make a second loaf.
Place on parchment paper on a cookie sheet. Brush loaves with the yolk of your remaining egg. Then either sprinkle seeds directly onto the loaf, or dip one finger in the egg wash, then in the seeds, and apply directly to the loaf.
Let loaves sit for 30 minutes, then put in a 350-degree oven and bake for 30 minutes.