First, make sure it's 80+ degrees out during the day (the hotter the better), necessitating the use of the air conditioner.
Next, make sure there's a windstorm that night, thereby forcing you to leave the windows closed all night so the house doesn't cool down.
Have the two year-old accustomed to sharing a room with her five year-old sister. If the five year-old snores, even better.
Then, have the wind create a wind tunnel right outside your daughters' bedroom window. (The five year-old will, of course, sleep through this, snoring peacefully away, so you won't have to worry about her, fortunately.)
In addition, make sure you set up a cat-sized WWF ring right outside their bedroom door, so the cats can practice their moves after being cooped up inside all night. It especially helps if you can get them to growl and hiss at each other.
Force (and I mean force) all of these things to coincide at exactly 3:00 am, thereby waking said two year-old up and sending her crying to your bedroom door. Bring her in bed with you.
Make sure you don't let her fall back to sleep; keep her awake at all costs. Flail your arms around her head, knocking gently into her every once in awhile. Whisper her name over and over until she answers you. Squiggle around until she spits out, "Go to sleep NOW!"
Have your husband drag her out of your bed at 5:00 am to watch him exercise. Have him force sugary Apple Jacks down her throat at 6:00 am. Make sure he keeps her occupied until he leaves for work, then prop her eyelids open so she can watch a Baby Einstein until her five year-old sister wakes up at 7:30 am.
After that, go about your business as usual, serving lunch at 11:10 am. At 11:30 pm, finished or not, cuddle your irascible, whiny, exhausted two year-old to your chest, change her diaper, rock her, sing to her, and put her in her crib with her books, blanket, and dolls. Tell her goodnight, and that you love her. Close the door and breathe a sigh of relief.
Don't hear another peep from her until after 4:00 pm.
That's how to wear out a two year-old.