Just got a Microwave for a friends '06 T2000 at Lowes, for 40 bucks. I can't remember what he paid for the fridge there - though I don't think it was over 100 bucks. I want to say it was around 80 bucks but don't quote me.
98 Freightliner that I trained in for Swift for 6 weeks had a 1500 watt inverter, it powered a small sized fridge and 600 watt microwave just fine. The TV ran on a seperate 2 outlet 150 watt inverter that plugged into an auxilary cigerette lighter plug in the sleeper. That small inverter ran the TV and laptop just fine.
Add a lockwasher to the battery terminal for a better positive connection. also, make sure you mount the negative to either the negative on the battery terminal or something steel on the truck... many truck sleepers are made of aluminum and you don't get a good ground usually with aluminum. Steel frame is much better.
The 1500 watt inverter at Pilot can be had for 120 bucks, digital microwave at Lowes for 40 bucks, and Fridge for less than 100. Or go dumpster diving and dig out a Coleman or Igloo electric cooler, clean it up, replace the motor for 20 bucks sold in a kit at most T/A's and you're set for keepin' your lunch meat cool.
BigBob