Tā méi zhǔnbèi hǎo jiù shàngchǎng, jiéguǒ chī le bùshǎo kǔtou.
He went on stage unprepared and ended up suffering quite a lot for it.
Tips
usage
吃苦头 is a separable verb-object phrase (离合词): you can split it as 吃了苦头, 吃过苦头, 吃了不少苦头. Compare with 吃苦 ('to bear hardship') which is more abstract - 吃苦头 specifically means suffering CONSEQUENCES from a bad choice or mistake.
memory
Literally 'eat the bitter end / eat a bit of bitterness' - 吃 'eat' + 苦 'bitter' + 头 'end/bit'. Chinese frames suffering as 'eating bitterness' (cf. 吃苦耐劳 'eat bitter, endure toil').
