Here are some synonyms for "What are you doing?" that you can use in different situations:

• What are you up to?
• Are you doing anything?
• Are you busy?
• Are you free?
• Do you have any spare time?
• Whats going on?
• Whats new?
• Whats happening?
• What are you at?
• What are you doing up there?
• What is your deal?
• What do you intend doing?
• What is the matter?
• What are you about?
• What do you do for fun?
• What is going down?
• What is up?
• How have you been?
• How goes it?
• How are things going?
• What are you doing these days?
• What are you doing lately?

In addition, here are some related phrases and words that you can use:

• Compliment
• Devoirs
• Did you hear what was passing?
• Did you see what was passing?
• Greetings
• Hello
• Hey
• Hi
• Int
• Accomplishment
• Act
• Action
• Deed
• Performance
• Thing
• Achieving
• Exploit
• Performing
• Carrying-out
• Execution
• Handiwork
• Implementation

Remember that the choice of synonym or related phrase depends on the context and the relationship you have with the person you are talking to.