Fasting may change the way you look at food and change some of your food choices, but that doesn't mean you can't (or won't want to!) eat treats on your feast days.
Eat what you like. Fruit. Veg. Pasta. Bread. Chocolate. Ice cream. Crisps. Cheese.
It doesn't matter! Most people won't vastly overeat consistantly on their feed days, it's just not possible to consume that many calories more than normal on a regular basis. So enjoy your food, and listen to your body.
Just remember that 'feast' doesn't mean over-eat, at least not all the time. Treats won't hurt, but if you're eating lots more than you usually would you're not going to lose weight. On your 'feast' days try to eat how you have always eaten, whatever is 'normal' for you. You may well find this reduces with time anyway.
I find that having done 5:2 for 5 months, I'm now more relaxed about what I eat on my feed days - and I have just as good results as when I started on 5:2 and was still restricting to 1400 cals on my feeds. My body tells me if I've eaten too much, and I do notice that if I eat a lot of chocolate etc that I don't feel so good. But that's a good thing as it stops me eating it to excess I mean, 3 bars of Guylian praline might have been too much in a row, haha!