Get the rocket and blast up to the top of grafitti tank. Pound the top to get a fruit. Note that you go left and right, one or the other is active at any point in time. They keep rotating through the fruits to whatever Yoshi wants. When you find what he wants, get it over to Yoshi to start out.

Note that his juice causes enemies to do different things:

yellow - stationary
pink - rise up
purple - float forwards

Get over to the cage using the enemies across the water, first to the spot to the left with a palm tree. To do this:

Go out on purple to ledge. Go up to palm tree. eat melon. now pink. Now when shoot they go up, go up ledges to cage. Spray off gunk, go up on cage, slam down and get the shine.

Super Mario Sunshine Walkthrough