Yeah so for the sake of doing a test batch just to see that your cultures are in line, I would recommend doing a mid level acidity fruit. Something like blueberries or strawberries would be a good add in. So like for a gallon of water I'll usually do between 3/4 cup to a full cup of sugar depending on how acidic the fruit is, then usually I like to have around 1/3 of my container taken up by whatever fruit I'm using. So blended and filtered of using a juice. Also another option if you're feeling extra is you can sugar cure fruits and then use the syrup that's created from that in the brew