I like to divide my 500 cals into 3 small meals; 150 for breakfast, 200 for lunch and 150 for supper. I use myfitnesspal to record my intake. Breakfast today was a nectarine, a large strawberry and 2 oatcakes with a tiny smear of Marmite; mfp says that's 141 cals.
I'm enjoying the challenge of finding good meals to make the most of 500 calories. For lunch today I'm planning a home-made chicken and rice soup which mfp says is 150 cals per portion, and I can freeze the other portions for later fast days.
Looking forward to sharing the journey with you all!