How do I simulate a bad Wi-Fi connection on my iPad?
There are a few ways you can do this, depending on your situation:


Move further away from your router. While this may seem a bit obvious, I realize that it isn't always possible while testing/debugging (for example, if you are working on a desktop computer).
Put aluminum foil around the router and/or antenna. This will (partially) block some or all of the radio signals by creating a makeshift Faraday cage. The results you get will depend on the strength of your router signal, distance from the router, and other environmental factors.
Set your router's wireless signal power to a lower setting. The method for doing this is different for each router, so you will have to look at the user guide for instructions on how to do this.


I hope this helps solve your problems!

EDIT:

Another thing I just thought about would be to make your SSID hidden. iDevices are known to have problems reconnecting to hidden networks, and you might be able to programmatically disconnect from the network at random intervals.