4 Pranks (untested read comments to see if they work or not)

Well i didn't test them but i always forget my ideas so i want to share these hope they work as i said never tested

1 Fake Coffee
If your sister drinks coffee add some chocolate water and a tiny dash of ketchup to her coffee while she isn't looking possibly some mustard in her milkshake

2 Soapy Knobs
Cover her doorknob in soap from the inside then leave hopefully she won't be able to get it open don't leave any paper towels in there and get her out after a hour and see the look on her face

3 Secret Recipe
Make her a pie but don't use lemons use mustard
Chocolate: Bake a crust then put ketchup and coffee mixed with chocolate syrup in it
Lemon: Bake crust and add mustard
Pistachio: add water lettuce leaves and flour to a bowl and mash them together to make a green mucky unwanted pie filling make sure it feels like pie filling and add a few pistachios then bake a crust when the crust is baked add all the unwanted green filling

4 No Water
Use water proof tape and put it where the water comes out hide your sisters perfume and deodorant and the cans of tomato juice(only hide the tomato juice and continue reading if you have a pet skunk that doesn't like your sister) find your skunk and spray her with it