There are flies in my ice cream!

The question says that each person likes a unique flavor, so let us see the statements one by one;

• Summer likes the Pink Peppercorn flavor, So let us place a dot in the grid.

$\begin{array}{|c|c|c|c|} \hline & \text{Chocolate} &\text{Green tea}& \text{Pink Peppercorn} \\ \hline \text{Summer} & \times & \times & • \\ \hline \text{Rick} & &\\ \hline \text{Morty}& & \\ \hline \end{array}$

• Rick doesn't like the Green Tea flavor, this statement indicates that he likes Chocolate, because, Summer likes pink peppercorn and he doesn't like green tea, so he must like the chocolate flavor.

And with this we can come to the conclusion that Morty should like the Green tea flavor, so the grid will look like this:

$\begin{array}{|c|c|c|c|} \hline & \text{Chocolate} &\text{Green tea}& \text{Pink Peppercorn}\\ \hline \text{Summer} & \times & \times & • \\ \hline \text{Rick} &• & \times & \times\\ \hline \text{Morty}& \times & • &\times \\ \hline \end{array}$

If Summer likes the pink peppercorn flavor ice cream and Rick doesn't likes the green tea flavor. So,

• Summer likes the pink peppercorn flavor ice cream

• Rick likes the chocolate flavor ice cream.

• $\color{#3D99F6} \boxed{\text{Morty likes the green tea flavor ice cream.}}$