juice. add sugar, lemon juice, yeast, and salt.
fill bottle with water, leaving at least an inch of space at top. remove funnel and screw cap on tightly. gently shake bottle to dissolve sugar. feel the bottle, and notice that it has a little bit of "give" (just for reference later). let stand at room temperature for 24-48 hours. at this point, when you try to squeeze the bottle again, it will no longer give, but instead feel hard and firm.
slowly unscrew the cap (to release gas), and if you like, use a funnel to transfer to other bottles or jars, leaving at least 1-inch of space at the top of 