A 5-year-old can mutate from charming to challenging in the blink of an eye. She wants to explore and assert her independence, and that is absolutely normal. However, watching her go from being extra helpful with chores one minute to loudly disagreeing with everything you say and do the next can give you whiplash. Fortunately, there are ways to fight the fresh talk while still supporting her spirit.
Try to determine why your child is talking back. She might be genuinely puzzled by your directions to do something, asserting her independence or modeling behavior she's seen from other children or on television. Don't overreact, but if she's being influenced by other children or television, explain that your home has different rules and, if necessary, monitor her friends and what television shows she watches.
Calmly tell your 5-year-old that talking to others that way is unacceptable, and if it happens again there will consequences. Be clear about what the consequences are, such as the loss of a favorite television show or toy for a period of time.
Explain how to disagree. While she may not get her way, stating why she is upset or disagrees with you rather than simply yelling "no" or "shut up" will provide better results. Maybe she doesn't want to clean up her toys because she is in the middle of a fun, imaginative game. If you know that, you can give her a 10-minute warning in the future.
Allow choices when possible. Don't negotiate when your 5-year-old talks back, but if you notice the tendency for back talk developing, start looking for small decisions she can make on her own. For example, offer two choices in clothing or dinner plans and let her make the final selection. Allowing her to feel in control of some things will minimize her need to be in control of everything.
Model good behavior. Don't get drawn into an argument, back-and-forth bickering or other bad behavior when your 5-year-old melts down. Simply state the consequences and follow through. Speak to her thoughtfully; if you commonly use a sarcastic tone with others, reign it in, since she's too young to realize that sort of talk isn't always acceptable.