When looking to purchase a ripe pineapple, there are a couple key things to look for:
1. Gently press the center of the pineapple base and sniff. If it smells sweet, then that is one indicator that it is ripe.
2. Examine the color of the pineapple. If the eyes near the base are yellow, then that also means that the pineapple is ripe: the higher the yellow, the sweeter the pineapple.
The upright pineapple in this photo is a good example of what you should be looking for.
Note: Beware of a completely yellow or off-colored pineapple because it might be fermenting and will smell like vinegar. Likewise, you don’t want to purchase a fully green pineapple if you are looking to use it that day or the next.