以下是我的回答，外研版六年级下册英语顺口溜，来一首简单的：

Apple, apple, red and round.

Juice, juice, sweet and tasty.

Cake, cake, soft and yummy.

Eat well, be healthy every day!

这首顺口溜描述了苹果的红和圆，果汁的甜和美味，蛋糕的柔软和好吃，最后提醒大家每天都要吃得健康。简单易懂，适合六年级的学生学习和记忆。