Cakes and Ale have three purposes:
1. As a means of giving thanks via eating
2. As a 'chill down' or grounding section of the ritual
3. As a means of giving thanks via libation

Of course, just because we call it cakes and ale doesn't mean that you have to have cakes and ale. You could have fruit juice, but I would advise that you only have something small to eat, like a cake or a bread roll or something similar to avoid feeling bloated.

Cakes and Ale should be Blessed (or consecrated) before consumption.

You can do this by either holding your athame, wand or hands over the top and imagining white light streaming out over them.

Say some words, if you like, such as these:
'I bless these cakes and ale in the name of the Goddess. May they be blessed with her love as I bless them with mine. So mote it be'

Save a small amount of the food and drink to use as a libation. If you are outside, this can be done before you eat and drink. If you are inside, wait until the ritual is over and then place the food on the ground and pour over the drink. Say some words as you do so, for example:

'I thank you Goddess for all I receive. I return this to you so that it may grow threefold.'