It would depend on the state of it.
If its really stained household thin bleach, non fragment like shop basic / value brand and a lots of water for rinsing it out afterward
If its just a normal good clean then what about soda crystals (from supermarket) , VWP, Chemipro OXI, see online brew shops for ideas.
Also sometimes a kettle of boiling water can help soften or remove some stuff.
Also things like a bottle brush, dish washing brush and wiping with kitchen roll can help remove crud.
There loads of things you can use for cleaning just be carfull to rinse then off well afterwards.