We did this for my children's school fall festival and used the orange soda bottles as a ring toss game:) All we used was bottles of orange soda, a black sharpie to make pumpkin faces and some plastic rings.
Squirt a small amount of paint in the bottom of each water bottle. Put the caps back on all your bottles. Shake each bottle vigorously to spread the paint all through the bottle. Remove cap and pour out any excess paint/water.