The time required to chill a can of room temperature Diet Coke in the freezer to a reasonably cold temperature without it becoming icy can vary depending on factors such as the initial temperature of the can, the freezer's temperature, and the desired level of coldness. However, a general guideline is to leave the can in the freezer for about 20 to 30 minutes.
If you leave the can in the freezer for too long, it may become icy and potentially burst due to the expansion of water as it freezes. So, it's essential to monitor the time and check on the can periodically. To speed up the chilling process, you can place the can in a container with some ice and water while it's in the freezer. The ice water will transfer its cold temperature more effectively to the can, allowing it to cool faster.
Again, these are general guidelines, and the exact time may vary depending on individual freezers and preferences. Always be cautious not to leave the can in the freezer for an extended period to avoid potential damage and mess from freezing. If you're unsure, it's better to take it out a bit early and let it cool further at room temperature if needed.